Genetics- the science of the laws of heredity and variability. The date of the “birth” of genetics can be considered 1900, when G. De Vries in Holland, K. Correns in Germany and E. Cermak in Austria independently “rediscovered” the laws of inheritance of traits established by G. Mendel back in 1865.

Heredity- the ability of organisms to transmit their characteristics from one generation to another.

Variability- the ability of organisms to acquire new characteristics compared to their parents. In a broad sense, variability refers to differences between individuals of the same species.

Sign- any structural feature, any property of the body. The development of a trait depends both on the presence of other genes and on environmental conditions; the formation of traits occurs during individual development individuals. Therefore, each individual individual has a set of characteristics characteristic only of it.

Phenotype- the totality of all external and internal signs of the body.

Gene- a functionally indivisible unit of genetic material, a section of a DNA molecule encoding the primary structure of a polypeptide, transfer or ribosomal RNA molecule. In a broad sense, a gene is a section of DNA that determines the possibility of developing a separate elementary trait.

Genotype- a set of genes of an organism.

Locus- location of the gene on the chromosome.

Allelic genes- genes located in identical loci of homologous chromosomes.

Homozygote- an organism that has allelic genes of one molecular form.

Heterozygote- an organism that has allelic genes of different molecular forms; in this case, one of the genes is dominant, the other is recessive.

Recessive gene- an allele that determines the development of a trait only in the homozygous state; such a trait will be called recessive.

Dominant gene- an allele that determines the development of a trait not only in a homozygous, but also in a heterozygous state; such a trait will be called dominant.

Genetics methods

The main one is hybridological method- a system of crossings that allows one to trace patterns of inheritance of traits over a series of generations. First developed and used by G. Mendel. Distinctive features method: 1) targeted selection of parents who differ in one, two, three, etc. pairs of contrasting (alternative) stable characteristics; 2) strict quantitative accounting of the inheritance of traits in hybrids; 3) individual assessment of the offspring from each parent in a series of generations.

Crossing in which the inheritance of one pair of alternative characters is analyzed is called monohybrid, two pairs - dihybrid, several pairs - polyhybrid. Alternative features mean different meanings of a feature, for example, the feature is the color of peas, alternative features are the color yellow, green color peas

In addition to the hybridological method, the following are used in genetics: genealogical- compilation and analysis of pedigrees; cytogenetic- study of chromosomes; twin- study of twins; population-statistical method - studying the genetic structure of populations.

Genetic symbolism

Proposed by G. Mendel, used to record the results of crossings: P - parents; F - offspring, the number below or immediately after the letter indicates the serial number of the generation (F 1 - first generation hybrids - direct descendants of parents, F 2 - second generation hybrids - arise as a result of crossing F 1 hybrids with each other); × - crossing icon; G - male; E - female; A is a dominant gene, a is a recessive gene; AA is a homozygote for a dominant, aa is a homozygote for a recessive, Aa is a heterozygote.

The law of uniformity of first generation hybrids, or Mendel's first law

The success of Mendel's work was facilitated by good choice object for crossing - different varieties of peas. Features of peas: 1) it is relatively easy to grow and has a short development period; 2) has numerous offspring; 3) has a large number of clearly visible alternative characters (corolla color - white or red; cotyledon color - green or yellow; seed shape - wrinkled or smooth; pod color - yellow or green; pod shape - round or constricted; arrangement of flowers or fruits - along the entire length of the stem or at its top; stem height - long or short); 4) is a self-pollinator, as a result of which it has a large number of pure lines that stably retain their characteristics from generation to generation.

Mendel conducted experiments on crossing different varieties of peas for eight years, starting in 1854. On February 8, 1865, G. Mendel spoke at a meeting of the Brunn Society of Naturalists with a report “Experiments on plant hybrids,” where the results of his work were summarized.

Mendel's experiments were carefully thought out. If his predecessors tried to study the patterns of inheritance of many traits at once, Mendel began his research by studying the inheritance of just one pair of alternative traits.

Mendel took pea varieties with yellow and green seeds and artificially cross-pollinated them: he removed the stamens from one variety and pollinated them with pollen from another variety. The first generation hybrids had yellow seeds. A similar picture was observed in crosses in which the inheritance of other traits was studied: when crossing plants with smooth and wrinkled seed shapes, all the seeds of the resulting hybrids were smooth; when crossing red-flowered plants with white-flowered plants, all the resulting ones were red-flowered. Mendel came to the conclusion that in first-generation hybrids, of each pair of alternative characters, only one appears, and the second seems to disappear. Mendel called the trait manifested in first-generation hybrids dominant, and the suppressed trait recessive.

At monohybrid cross homozygous individuals having different meanings alternative traits, hybrids are uniform in genotype and phenotype.

Genetic diagram of Mendel's law of uniformity

(A - yellow color of peas, a - green color of peas)

Law of segregation, or Mendel's second law

G. Mendel gave the first generation hybrids the opportunity to self-pollinate. The second generation hybrids obtained in this way showed not only a dominant, but also a recessive trait. The experimental results are shown in the table.

Signs	Dominant		Recessive		Total
	Number	%	Number	%
Seed shape	5474	74,74	1850	25,26	7324
Cotyledon color	6022	75,06	2001	24,94	8023
Seed coat color	705	75,90	224	24,10	929
Bob shape	882	74,68	299	25,32	1181
Bob coloring	428	73,79	152	26,21	580
Flower arrangement	651	75,87	207	24,13	858
Stem height	787	73,96	277	26,04	1064
Total:	14949	74,90	5010	25,10	19959

Analysis of the table data allowed us to draw the following conclusions:

1. uniformity of hybrids in the second generation is not observed: some hybrids carry one (dominant), some - another (recessive) trait from an alternative pair;
2. the number of hybrids carrying a dominant trait is approximately three times greater than the number of hybrids carrying a recessive trait;
3. The recessive trait does not disappear in the first generation hybrids, but is only suppressed and appears in the second hybrid generation.

The phenomenon in which part of the second generation hybrids carries a dominant trait, and part - a recessive one, is called splitting. Moreover, the splitting observed in hybrids is not random, but is subject to certain quantitative patterns. Based on this, Mendel made another conclusion: when crossing hybrids of the first generation, the characteristics in the offspring are split in a certain numerical ratio.

At monohybrid crossing of heterozygous individuals in hybrids there is a cleavage according to phenotype in a ratio of 3:1, according to genotype 1:2:1.

Genetic diagram of Mendel's law of segregation

(A - yellow color of peas, and - green color of peas):

P	♀Aa yellow		×	♂Aa yellow
Types of gametes	A	a		A	a
F 2	A.A. yellow	Aa yellow 75%		Aa yellow	aa green 25%

Law of gamete purity

From 1854, for eight years, Mendel conducted experiments on crossing pea plants. He discovered that as a result of crossing different varieties of peas with each other, the first generation hybrids have the same phenotype, and in the second generation hybrids, the characteristics are split in certain proportions. To explain this phenomenon, Mendel made a number of assumptions, which were called the “gamete purity hypothesis”, or the “gamete purity law”. Mendel suggested that:

1. some discrete hereditary factors are responsible for the formation of traits;
2. organisms contain two factors that determine the development of a trait;
3. during the formation of gametes, only one of a pair of factors enters each of them;
4. when male and female gametes merge, these hereditary factors do not mix (remain pure).

In 1909, V. Johansen called these hereditary factors genes, and in 1912, T. Morgan showed that they are located in chromosomes.

To prove his assumptions, G. Mendel used crossing, which is now called analyzing ( test cross- crossing an organism of an unknown genotype with an organism homozygous for a recessive). Perhaps Mendel reasoned in the following way: “If my assumptions are correct, then as a result of crossing F 1 with a variety that has a recessive trait (green peas), among the hybrids there will be half green peas and half yellow peas.” As can be seen from the genetic diagram below, he actually received a 1:1 split and was convinced of the correctness of his assumptions and conclusions, but he was not understood by his contemporaries. His report “Experiments on plant hybrids,” made at a meeting of the Brunn Society of Naturalists, was met with complete silence.

Cytological basis of Mendel's first and second laws

At the time of Mendel, the structure and development of germ cells had not been studied, so his hypothesis of the purity of gametes is an example of brilliant foresight, which later found scientific confirmation.

The phenomena of dominance and segregation of characters observed by Mendel are currently explained by the pairing of chromosomes, the divergence of chromosomes during meiosis and their unification during fertilization. Let us denote the gene that determines the yellow color by the letter A, and the green color by a. Since Mendel worked with pure lines, both organisms crossed are homozygous, that is, they carry two identical alleles of the seed color gene (AA and aa, respectively). During meiosis, the number of chromosomes is halved, and only one chromosome from a pair ends up in each gamete. Since homologous chromosomes carry the same alleles, all gametes of one organism will contain a chromosome with gene A, and the other - with gene a.

During fertilization, the male and female gametes fuse and their chromosomes combine to form a single zygote. The resulting hybrid becomes heterozygous, since its cells will have the Aa genotype; one variant of the genotype will give one variant of the phenotype - the yellow color of peas.

In a hybrid organism that has the Aa genotype during meiosis, the chromosomes diverge into different cells and two types of gametes are formed - half of the gametes will carry gene A, the other half will carry gene a. Fertilization is a random and equally probable process, that is, any sperm can fertilize any egg. Since two types of sperm and two types of eggs were formed, four types of zygotes are possible. Half of them are heterozygotes (carry the A and a genes), 1/4 are homozygous for a dominant trait (carry two A genes) and 1/4 are homozygous for a recessive trait (carry two a genes). Homozygotes for the dominant and heterozygotes will produce yellow peas (3/4), homozygotes for the recessive - green (1/4).

The law of independent combination (inheritance) of characteristics, or Mendel's third law

Organisms differ from each other in many ways. Therefore, having established the patterns of inheritance of one pair of traits, G. Mendel moved on to studying the inheritance of two (or more) pairs of alternative traits. For di hybrid crossing Mendel took homozygous pea plants that differed in seed color (yellow and green) and seed shape (smooth and wrinkled). The yellow color (A) and smooth shape (B) of the seeds are dominant traits, the green color (a) and wrinkled shape (b) are recessive traits.

By crossing a plant with yellow and smooth seeds with a plant with green and wrinkled seeds, Mendel obtained a uniform hybrid generation F 1 with yellow and smooth seeds. From self-pollination of 15 first-generation hybrids, 556 seeds were obtained, of which 315 were yellow smooth, 101 yellow wrinkled, 108 green smooth and 32 green wrinkled (splitting 9:3:3:1).

Analyzing the resulting offspring, Mendel drew attention to the fact that: 1) along with combinations of characteristics of the original varieties (yellow smooth and green wrinkled seeds), during dihybrid crossing new combinations of characteristics appear (yellow wrinkled and green smooth seeds); 2) splitting for each individual trait corresponds to splitting during monohybrid crossing. Of the 556 seeds, 423 were smooth and 133 wrinkled (ratio 3:1), 416 seeds were yellow in color, and 140 were green (ratio 3:1). Mendel came to the conclusion that splitting in one pair of traits is not associated with splitting in the other pair. Hybrid seeds are characterized not only by combinations of characteristics of parent plants (yellow smooth seeds and green wrinkled seeds), but also by the emergence of new combinations of characteristics (yellow wrinkled seeds and green smooth seeds).

When dihybrid crossing diheterozygotes in hybrids, there is a cleavage according to the phenotype in the ratio 9:3:3:1, according to the genotype in the ratio 4:2:2:2:2:1:1:1:1, the characters are inherited independently of each other and are combined in all possible combinations.

R	♀AABB yellow, smooth	×	♂aаbb green, wrinkled
Types of gametes	AB		ab
F 1	AaBb yellow, smooth, 100%
P	♀AaBb yellow, smooth	×	♂AаBb yellow, smooth
Types of gametes	AB Ab aB ab		AB Ab aB ab

Genetic scheme of the law of independent combination of traits:

	♂	AB	Ab	aB	ab
♀
AB		AABB yellow smooth	AABb yellow smooth	AaBB yellow smooth	AaBb yellow smooth
Ab		AABb yellow smooth	AAbb yellow wrinkled	AaBb yellow smooth	Aabb yellow wrinkled
aB		AaBB yellow smooth	AaBb yellow smooth	aaBB green smooth	aaBb green smooth
ab		AaBb yellow smooth	Aabb yellow wrinkled	aaBb green smooth	aabb green wrinkled

Analysis of crossbreeding results by phenotype: yellow, smooth - 9/16, yellow, wrinkled - 3/16, green, smooth - 3/16, green, wrinkled - 1/16. Phenotype splitting is 9:3:3:1.

Analysis of crossbreeding results by genotype: AaBb - 4/16, AABb - 2/16, AaBB - 2/16, Aabb - 2/16, aaBb - 2/16, AABB - 1/16, Aabb - 1/16, aaBB - 1/16, aabb - 1/16. Segregation by genotype 4:2:2:2:2:1:1:1:1.

If in a monohybrid crossing the parent organisms differ in one pair of characters (yellow and green seeds) and give in the second generation two phenotypes (2 1) in the ratio (3 + 1) 1, then in a dihybrid they differ in two pairs of characters and give in the second generation four phenotypes (2 2) in the ratio (3 + 1) 2. It is easy to calculate how many phenotypes and in what ratio will be formed in the second generation during a trihybrid cross: eight phenotypes (2 3) in the ratio (3 + 1) 3.

If the splitting by genotype in F 2 with a monohybrid generation was 1: 2: 1, that is, there were three different genotypes (3 1), then with a dihybrid crossing 9 different genotypes are formed - 3 2, with a trihybrid crossing 3 3 - 27 different genotypes are formed.

Mendel's third law is valid only for those cases when the genes for the analyzed traits are located in different pairs of homologous chromosomes.

Cytological basis of Mendel's third law

Let A be the gene that determines the development of yellow color of seeds, a - green color, B - smooth shape of the seed, b - wrinkled. First generation hybrids with genotype AaBb are crossed. During the formation of gametes, from each pair of allelic genes, only one gets into the gamete, and as a result of random divergence of chromosomes in the first division of meiosis, gene A can end up in the same gamete with gene B or gene b, and gene a - with gene B or gene b. Thus, each organism produces four types of gametes in the same quantity (25%): AB, Ab, aB, ab. During fertilization, each of the four types of sperm can fertilize any of the four types of eggs. As a result of fertilization, nine genotypic classes may appear, which will give rise to four phenotypic classes.

Chained inheritance

In 1906, W. Bateson and R. Punnett, crossing plants sweet pea and analyzing the inheritance of pollen shape and flower color, they found that these characters do not give independent distribution in the offspring; hybrids always repeated the characters of the parental forms. It became clear that not all traits are characterized by independent distribution in the offspring and free combination.

Each organism has a huge number of characteristics, but the number of chromosomes is small. Consequently, each chromosome carries not one gene, but a whole group of genes responsible for the development of different traits. He studied the inheritance of traits whose genes are localized on one chromosome. T. Morgan. If Mendel conducted his experiments on peas, then for Morgan the main object was fruit fly Drosophila.

Drosophila produces numerous offspring every two weeks at a temperature of 25 °C. The male and female are clearly distinguishable in appearance - the male's abdomen is smaller and darker. They have only 8 chromosomes in a diploid set and reproduce quite easily in test tubes on an inexpensive nutrient medium.

By crossing a Drosophila fly with a gray body and normal wings with a fly having a dark body color and rudimentary wings, in the first generation Morgan obtained hybrids with a gray body and normal wings (the gene that determines the gray color of the abdomen dominates the dark color, and the gene that determines development of normal wings, - above the gene of underdeveloped wings). When carrying out an analytical crossing of an F 1 female with a male who had recessive traits, it was theoretically expected to obtain offspring with combinations of these traits in a ratio of 1:1:1:1. However, individuals with characteristics of the parental forms clearly predominated in the offspring (41.5% - gray long-winged and 41.5% - black with rudimentary wings), and only a small part of the flies had a combination of characters different from those of the parents (8.5% - black long-winged and 8.5% - gray with rudimentary wings). Such results could only be obtained if the genes responsible for body color and wing shape are located on the same chromosome.

1 - non-crossover gametes; 2 - crossover gametes.

If the genes for body color and wing shape are localized on one chromosome, then this crossing should have resulted in two groups of individuals repeating the characteristics of the parental forms, since the maternal organism should form gametes of only two types - AB and ab, and the paternal organism - one type - ab . Consequently, two groups of individuals with the genotype AABB iaabb should be formed in the offspring. However, individuals appear in the offspring (albeit in small numbers) with recombined traits, that is, having genotypes Aabb and aaBb. In order to explain this, it is necessary to recall the mechanism of formation of germ cells - meiosis. In the prophase of the first meiotic division, homologous chromosomes are conjugated, and at this moment an exchange of regions can occur between them. As a result of crossing over, in some cells, sections of chromosomes are exchanged between genes A and B, gametes Ab and aB appear, and, as a result, four groups of phenotypes are formed in the offspring, as with the free combination of genes. But, since crossing over occurs during the formation of a small part of gametes, the numerical ratio of phenotypes does not correspond to the ratio 1:1:1:1.

Clutch group- genes localized on the same chromosome and inherited together. The number of linkage groups corresponds to the haploid set of chromosomes.

Chained inheritance- inheritance of traits whose genes are localized on one chromosome. The strength of linkage between genes depends on the distance between them: the further the genes are located from each other, the higher the frequency of crossing over and vice versa. Full grip- a type of linked inheritance in which the genes of the analyzed traits are located so close to each other that crossing over between them becomes impossible. Incomplete clutch- a type of linked inheritance in which the genes of the analyzed traits are located at a certain distance from each other, which makes crossing over between them possible.

Independent inheritance- inheritance of traits whose genes are localized in different pairs of homologous chromosomes.

Non-crossover gametes- gametes during the formation of which crossing over did not occur.

Gametes are formed:

Crossover gametes- gametes in the process of formation of which crossing over occurred. As a rule, crossover gametes make up a small part of the total number of gametes.

Gametes are formed:

Non-recombinants- hybrid individuals that have the same combination of characteristics as their parents.

Recombinants- hybrid individuals that have a different combination of characteristics than their parents.

The distance between genes is measured in Morganids - conventional units, corresponding to the percentage of crossover gametes or the percentage of recombinants. For example, the distance between the genes for gray body color and long wings (also black body color and rudimentary wings) in Drosophila is 17%, or 17 morganids.

In diheterozygotes, dominant genes can be located either on one chromosome ( cis phase), or in different ( trans phase).

1 - Cis-phase mechanism (non-crossover gametes); 2 - trans-phase mechanism (non-crossover gametes).

The result of T. Morgan's research was the creation of chromosomal theory of heredity:

1. genes are located on chromosomes; different chromosomes contain different numbers of genes; the set of genes of each of the non-homologous chromosomes is unique;
2. each gene has a specific location (locus) on the chromosome; allelic genes are located in identical loci of homologous chromosomes;
3. genes are located on chromosomes in a specific linear sequence;
4. genes localized on the same chromosome are inherited together, forming a linkage group; the number of linkage groups is equal to the haploid set of chromosomes and is constant for each type of organism;
5. gene linkage can be disrupted during crossing over, which leads to the formation of recombinant chromosomes; the frequency of crossing over depends on the distance between genes: the greater the distance, the greater the magnitude of crossing over;
6. Each species has a unique set of chromosomes - a karyotype.

Genetics of sex

Chromosomal sex determination

Most animals are dioecious organisms. Sex can be considered as a set of characteristics and structures that provide a method of reproduction of offspring and the transmission of hereditary information. Sex is most often determined at the moment of fertilization, that is, in sex determination main role plays the karyotype of the zygote. The karyotype of each organism contains chromosomes that are the same in both sexes - autosomes, and chromosomes on which the female and male sexes differ from each other - sex chromosomes. In humans, the “female” sex chromosomes are two X chromosomes. When gametes are formed, each egg receives one of the X chromosomes. A sex that produces gametes of the same type, carrying the X chromosome, is called homogametic. In humans, the female sex is homogametic. The “male” sex chromosomes in humans are the X chromosome and the Y chromosome. When gametes are formed, half of the sperm receives an X chromosome, the other half receives a Y chromosome. Sex that produces gametes different types, is called heterogametic. In humans, the male sex is heterogametic. If a zygote is formed that carries two X chromosomes, then it will form female body, if the X chromosome and Y chromosome are male.

In animals the following can be distinguished: four types chromosomal determination gender.

1. The female sex is homogametic (XX), the male is heterogametic (XY) (mammals, in particular, humans, Drosophila).

   Genetic scheme of chromosomal sex determination in humans:

   R	♀46,XX	×	♂46,XY
   Types of gametes	23, X		23, X 23, Y
   F	46, XX females, 50%		46,XY males, 50%

   Genetic scheme of chromosomal sex determination in Drosophila:

   R	♀8, XX	×	♂8, XY
   Types of gametes	4, X		4, X 4, Y
   F	8, XX females, 50%		8,XY males, 50%

2. The female sex is homogametic (XX), the male sex is heterogametic (X0) (Orthoptera).

   Genetic scheme of chromosomal sex determination in the desert locust:

   R	♀24, XX	×	♂23, X0
   Types of gametes	12, X		12.X 11.0
   F	24, XX females, 50%		23, X0 males, 50%

3. The female sex is heterogametic (XY), the male sex is homogametic (XX) (birds, reptiles).

   Genetic scheme of chromosomal sex determination in a pigeon:

   R	♀80,XY	×	♂80,XX
   Types of gametes	40, X 40, Y		40, X
   F	80,XY females, 50%		80, XX males, 50%

4. The female sex is heterogametic (X0), the male sex is homogametic (XX) (some types of insects).

   Genetic scheme of chromosomal sex determination in moths:

   R	♀61, X0	×	♂62,XX
   Types of gametes	31, X 30, Y		31, X
   F	61, X0 females, 50%		62, XX males, 50%

Inheritance of sex-linked traits

It has been established that sex chromosomes contain genes responsible not only for the development of sexual characteristics, but also for the formation of non-sexual characteristics (blood clotting, color of tooth enamel, sensitivity to red and green colors, etc.). The inheritance of non-sexual characteristics, the genes of which are localized on the X or Y chromosomes, is called sex-linked inheritance.

T. Morgan studied the inheritance of genes localized on sex chromosomes.

In Drosophila, red eye color is dominant over white. Reciprocal crossing- two crossings, which are characterized by a mutually opposite combination of the analyzed trait and sex in the forms taking part in this crossing. For example, if in the first crossing the female had a dominant trait and the male had a recessive trait, then in the second crossing the female should have a recessive trait and the male should have a dominant one. Carrying out reciprocal crossing, T. Morgan obtained the following results. When red-eyed females were crossed with white-eyed males in the first generation, all offspring turned out to be red-eyed. If you cross F1 hybrids with each other, then in the second generation all the females turn out to be red-eyed, and among the males, half are white-eyed and half are red-eyed. If you cross white-eyed females and red-eyed males, then in the first generation all the females turn out to be red-eyed, and the males are white-eyed. In F 2, half of the females and males are red-eyed, half are white-eyed.

T. Morgan was able to explain the results of the observed splitting in eye color only by assuming that the gene responsible for eye color is localized on the X chromosome (X A - red eye color, X a - White color eyes), and the Y chromosome does not contain such genes.

Diagram of human sex chromosomes and genes linked to them:
1 - X chromosome; 2 - Y chromosome.

In humans, a man receives an X chromosome from his mother and a Y chromosome from his father. A woman receives one X chromosome from her mother and another X chromosome from her father. X chromosome is medium submetacentric, Y chromosome is small acrocentric; The X chromosome and Y chromosome have not only different sizes, structure, but also for the most part carry different sets of genes. Depending on the gene composition in human sex chromosomes, the following regions can be distinguished: 1) non-homologous region of the X chromosome (with genes found only on the X chromosome); 2) a homologous region of the X chromosome and the Y chromosome (with genes present on both the X chromosome and the Y chromosome); 3) a non-homologous section of the Y chromosome (with genes found only on the Y chromosome). Depending on the location of the gene, the following types of inheritance are distinguished.

Inheritance type	Gene localization	Examples
X-linked recessive		Hemophilia, different shapes color blindness (protanopia, deuteronopia), absence of sweat glands, some forms muscular dystrophy etc.
X-linked dominant	Non-homologous region of the X chromosome	Brown tooth enamel, vitamin D resistant rickets, etc.
X-Y - linked (partially linked to the floor)	Homologous region of the X and Y chromosomes	Alport syndrome, general color blindness
Y-linked	Non-homologous region of the Y chromosome	Webbed toes, hypertrichosis of the auricular margin

Most of the genes linked to the X chromosome are absent on the Y chromosome, so these genes (even recessive ones) will manifest themselves phenotypically, since they are represented in the singular in the genotype. Such genes are called hemizygous. The human X chromosome contains a number of genes, the recessive alleles of which determine the development of severe anomalies (hemophilia, color blindness, etc.). These anomalies are more common in men (since they are hemizygous), although the carrier of the genes causing these anomalies is more often a woman. For example, if X A X A Y

F 2X A X A X A X a
♀ ok. roll blood
50% X A Y
♂ ok. roll blood
25% X a Y
♂ hemophiliacs
25%

MUNICIPAL BUDGET EDUCATIONAL INSTITUTION

"SECONDARY SCHOOL No. 1"

TEST ON THE TOPIC

"GENETICS"

(theoretical part)

tests in the form of the Unified State Exam

GENERAL BIOLOGY

9 – 11 CLASS

prepared

biology teacher

Andreeva Elvira Yurievna

Norilsk – 2010

Test option No. 1

(topic “Genetics”)

The test consists of 3 parts.

round

bbAA 3) BBAA BbAA 4) BbAb

round red

3:1 3) 1:1 9:3:3:1 4) 6:3

A9. When crossing night beauty plants with red and white flowers, hybrid offspring with pink flowers appear as a result of:

Test option No. 2

(topic “Genetics”)

The test consists of 3 parts.

The first part contains questions under the letter A. In them you need to choose only one correct answer.

The second part contains questions under the letter B. These tasks can be:

or to choose several correct answers;

tasks to establish correspondences of positions between processes and objects, as well as a description of their properties and characteristics;

tasks to determine the sequence of biological phenomena or processes

The third part (under the letter “C”) includes a detailed answer to the question posed.

AA 3) ab Aa 4) aa

(law A corresponds to - ...; and law B corresponds to - ...)

C2. Give a detailed answer to the following question. Construct a 2:8 Punnett lattice with your own characteristics, write down all possible phenotypes

Test option No. 3

(topic “Genetics”)

The test consists of 3 parts.

The first part contains questions under the letter A. In them you need to choose only one correct answer.

The second part contains questions under the letter B. These tasks can be:

or to choose several correct answers;

tasks to establish correspondences of positions between processes and objects, as well as a description of their properties and characteristics;

tasks to determine the sequence of biological phenomena or processes

The third part (under the letter “C”) includes a detailed answer to the question posed.
round red

bbAA 3) BBAA BbAA 4) BbAb

phenotype 3) genotype epistasis 4) allelopathy

(law A corresponds to - ...; and law B corresponds to - ...)

Test option No. 4

(topic “Genetics”)

The test consists of 3 parts.

The first part contains questions under the letter A. In them you need to choose only one correct answer.

The second part contains questions under the letter B. These tasks can be:

or to choose several correct answers;

tasks to establish correspondences of positions between processes and objects, as well as a description of their properties and characteristics;

tasks to determine the sequence of biological phenomena or processes

The third part (under the letter “C”) includes a detailed answer to the question posed.

9:3:3:1 3) 3:1 !:2:1 4) 1:1

AABb 3) AaBB AaBb 4) aaBB

Test option No. 5

(topic “Genetics”)

The test consists of 3 parts.

The first part contains questions under the letter A. In them you need to choose only one correct answer.

The second part contains questions under the letter B. These tasks can be:

or to choose several correct answers;

tasks to establish correspondences of positions between processes and objects, as well as a description of their properties and characteristics;

tasks to determine the sequence of biological phenomena or processes

A1. Chromosomes that are the same in shape and size and carry the same genes are called:

sister 3) homologous alternative 4) allelic

A2. Mendel developed a method:

monohybrid 3) hybridological dihybrid 4) heterosis

A3. A homozygous monohybrid cross is written as follows:

AA x aa 3) AABB x vvaa Aa x aa 4) AaVa x aavv

A4. If a change in a trait that occurs in an organism is not inherited, it means:

only genes have changed, not chromosomes, only chromosomes have changed, not genes genes and chromosomes have not changed, both genes and chromosomes have not changed

A5. When crossing homozygous tomato plants with round yellow fruits and with pear-shaped red fruits you will get offspring with the genotype:

bbAA 3) BBAA BbAA 4) BbAb

A6. If genes are located in different pairs of non-homologous chromosomes, then the law appears:

incomplete dominance 3) independent inheritance of complete dominance 4) splitting of characters

A7. When crossing heterozygous tomato plants with round red fruits and with individuals recessive for both characteristics, the offspring will be with genotypes AaBb and aabb in the ratio:

3:1 3) 1:1 9:3:3:1 4) 6:3

A8. When crossing homozygous night beauty plants with red and white flowers, intermediate inheritance is observed in the offspring, as it occurs:

gene linkage 3) gene interaction independent gene distribution 4) multiple gene action

A9. When crossing night beauty plants with red and white flowers, hybrid offspring with pink flowers appear as a result of:

linked inheritance 3) independent inheritance of character splitting 4) incomplete dominance

A10. A significant proportion of mutations do not appear in the offspring, since they:
1) are not associated with changes in genes 3) are dominant in nature 2) are not associated with changes in chromosomes 4) are recessive in nature
A11. The totality of all internal features is:

phenotype 3) genotype epistasis 4) allelopathy

A12. The limits within which changes in the characteristics of a genotype are possible are called:

reaction norm 3) modification by phenotype 4) mutation

IN 1. Establish a correspondence between Mendel's first and second laws and their characteristics

(law A corresponds to - ...; and law B corresponds to - ...)

homozygous crossing A. I Mendel's law heterozygous crossing B. II Mendel's law parents are pure lines parents are taken from F 1 splitting according to the phenotype 3: 1 in F 1 only heterozygous

C1. Give a detailed answer to the following question. What is the analyzed cross used for?
C2. Give a detailed answer to the following question. What method is used to identify the causes of Down syndrome?

Test option No. 6

(topic “Genetics”)

The test consists of 3 parts.

The first part contains questions under the letter A. In them you need to choose only one correct answer.

The second part contains questions under the letter B. These tasks can be:

or to choose several correct answers;

tasks to establish correspondences of positions between processes and objects, as well as a description of their properties and characteristics;

tasks to determine the sequence of biological phenomena or processes

The third part (under the letter “C”) includes a detailed answer to the question posed.
A1. The totality of all the genes of one organism is:

genome 3) gene pool genotype 4) karyotype

A2. The crossing of two organisms is called:

reproduction 3) reproduction fertilization 4) hybridization

A3. A dihybrid homozygous cross is written as follows:

AA x aa 3) AABB x aavv Aa x aa 4) AaBa x AaBv

A4. To determine the unknown genotype, a cross is made:

monohybrid 3) heterozygous dihybrid 4) analyzing

A5. The appearance of all offspring with the same phenotype and the same genotype indicates the manifestation of the law:

splitting 3) independent inheritance of dominance 4) linked inheritance

A6. Impact x-rays can cause in the cell:

relative variability 3) gene mutations combinative variability 4) adaptability to the environment

A7. When hybrids reproduce in offspring in F 2, a split in characteristics occurs, since:

individuals differ in genotype; individuals exhibit mutational variability; individuals differ in genotype; individuals exhibit modificational variability

A8. With intermediate inheritance of a trait in first-generation hybrids, the genotype looks like this:

AA 3) ab Aa 4) aa

A9. The interaction of allelic genes is the reason:

intermediate inheritance 3) independent inheritance linked inheritance 4) uniformity of offspring

A10. In the case when a dominant gene completely suppresses the action of a recessive gene, the law appears in the offspring:

splitting 3) intermediate inheritance dominance 4) independent inheritance

A11. What explains the manifestation of incomplete dominance in the first hybrid generation?

all individuals have a dominant trait all individuals have a recessive trait all individuals have an intermediate trait all individuals have the same trait

A12. Hereditary variability affects:

reaction norm 3) genotype of somatic cells genotype of germ cells 4) phenotype

IN 1. Establish the relationship between Mendel's first and third laws

(law A corresponds to - ...; and law B corresponds to - ...)

heterozygous crossing character splitting according to the 9:3:3:1 phenotype in F 1 only heterozygous homozygous crossing characters are inherited independently of each other parents are most often determined by analyzed crossing

A. I Mendel's lawB. Mendel's III law

C1. Give a detailed answer to the following question. Where are the genes for sex-linked traits?
C2. Give a detailed answer to the following question. Construct a 2:4 Punnett lattice with your own characteristics, write down all possible phenotypes

Test option No. 7

(topic “Genetics”)

The test consists of 3 parts.

The first part contains questions under the letter A. In them you need to choose only one correct answer.

The second part contains questions under the letter B. These tasks can be:

or to choose several correct answers;

tasks to establish correspondences of positions between processes and objects, as well as a description of their properties and characteristics;

tasks to determine the sequence of biological phenomena or processes

The third part (under the letter “C”) includes a detailed answer to the question posed.
A1. The totality of all the characteristics of one organism is:

genome 3) gene pool genome 4) phenotype

A2. Mutually exclusive, contrasting characteristics are called:

homologous 3) allelic linked 4) alternative

A3. A dihybrid heterozygous cross is written as follows:

AA x aa 3) AABB x vvaa Aa x aa 4) AaBa x AaBv

A4. Genes located at identical loci on homologous chromosomes are called:

allelic 3) dominant linked 4) recessive

A5. Crossing between individuals different types and childbirth is called:

heterosis 3) analyzed crossing by distant hybridization 4) polyploidy

A6. When crossing homozygous tomato plants with round red fruits and with pear-shaped yellow fruits, offspring with the genotype will be obtained:

bbAA 3) BBAA BbAA 4) BbAb

A7. If genes are located in different pairs of non-homologous chromosomes, then the law appears:

complete dominance 3) analyzed crossing of independent inheritance 4) splitting of characters

A8. In determining the sex of a person, the man plays a decisive role, since female gametes contain:

only X chromosomes, and male X and Y chromosomes X and Y chromosomes, and male only X chromosomes only Y chromosomes, and male X and Y chromosomes only Y chromosomes, and male X chromosomes

A9. Modification changes do not play a big role in evolution, since they:

are widespread 3) do not affect the phenotype; occur in individual individuals 4) are not inherited

A10. If a mutation that occurs in an organism is inherited, it means:

all proposed 3) chromosomal gene 4) genomic

A11. The totality of all spring signs is:

phenotype 3) genotype epistasis 4) allelopathy

A12. By depicting chromosomes, we depict:

genome 3) karyotype genotype 4) gene pool

IN 1. Establish a correspondence between Mendel’s second and third laws and their characteristics:

(law A corresponds to - ...; and law B corresponds to - ...)

splitting by phenotype 1:2:1 A. II Mendel's law heterozygous crossing B. III Mendel's law splitting of traits by phenotype 3:1 splitting of traits by phenotype 9:3:3:1 is used in selection for more complex operations homozygous crossing

C1. Give a detailed answer to the following question. Due to what processes can gene linkage be disrupted?
C2. Give a detailed answer to the following question. New to learn hereditary diseases.

Test option No. 8

(topic “Genetics”)

The test consists of 3 parts.

The first part contains questions under the letter A. In them you need to choose only one correct answer.

The second part contains questions under the letter B. These tasks can be:

or to choose several correct answers;

tasks to establish correspondences of positions between processes and objects, as well as a description of their properties and characteristics;

tasks to determine the sequence of biological phenomena or processes

The third part (under the letter “C”) includes a detailed answer to the question posed.
A1. The functional unit of genetic material is:

cell 3) chromosome gene 4) nucleus

A2. If a set of chromosomes contains a pair with identical chromosomes, then this pair is called

heterozygote 3) homozygote allelic gene 4) linked gene

A3. A monohybrid heterozygous cross is written as follows:

Aa x Aa 3) AaBB x vvaa Aa x aa 4) AaBa x Aavv

A4. The development of the offspring is significantly influenced by the following that occurred in the parents: 1) modification changes 3) gene mutations 2) somatic mutations 4) age-related changes
A5. In night beauty hybrids with pink flowers in F 2 plants with red, pink and white flowers appear in the ratio:

9:3:3:1 3) 3:1 !:2:1 4) 1:1

A6. When crossing Drosophila with a gray body and normal wings and Drosophila with a dark body and rudimentary wings, the law of linked inheritance appears, since the genes responsible for it:

located on different chromosomes 3) located on the same chromosome have undergone mutations 4) exhibit interaction

A7. The modification variability of a trait depends on:

age of the organism 3) environmental conditions at the stage of ontogenesis 4) genotype

A8. When crossing guinea pigs with genotypes Aabb x aaBB, offspring with the genotype will be obtained:

AABb 3) AaBB AaBb 4) aaBB

A9. If the genes responsible for the development of several traits are located on the same chromosome, then the law appears:

splitting 3) independent inheritance independent inheritance 4) linked inheritance

A10. The ability to predict the appearance of certain traits in individuals of related species appeared with the discovery of the law:

splitting 3) independent inheritance of genes of linked inheritance 4) homologous series in inheritance

A11. The F2 segregation ratio for a hybrid cross is:

12:3:1 3) 9:3:3:1 9:6:1 4) 1:1:1:1

A12. What disease can a son inherit if the father is colorblind and the mother is a carrier of hemophilia?

color blindness 3) both diseases hemophilia 4) will be healthy

IN 1. Establish a correspondence between Mendel's first and second laws and their characteristics:

in F 1 only heterozygous character splitting can be 1:2:1 or 3:1 homozygous crossing parents are pure lines conduct the analyzed crossing splitting according to the phenotype 9:3:3:1

A. I Mendel's lawB. Mendel's II law

C1. Give a detailed answer to the following question. What are the main methods used in genetic research?
C2. Give a detailed answer to the following question. How are genotype and phenotype related?

Answer key for genetics tests.

question number

14.11.2011

Christie

9 correct answers out of 11

25.11.2011

Shatalova, Stoiko, Chernikhovsky

9 correct answers out of 11
Your level of knowledge on the topic is 81.82%

25.11.2011

Chernikhovsky

10 correct answers out of 11

25.11.2011

Chernikhovsky

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

28.11.2011

Serbaeva M 11
10 correct answers out of 11

28.11.2011

Nikita Book

7 correct answers out of 11

29.11.2011

Kotkov 9g 9 correct answers out of 11
Your level of knowledge on the topic is 81.82%

29.11.2011

Yuryev Vova

10 correct answers out of 11

29.11.2011

Zelenov

7 correct answers out of 11
Your level of knowledge on the topic is 63.64%

29.11.2011

Osipova

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

29.11.2011

Alyona

Avakyan 9G 8 correct answers out of 11

29.11.2011

Rolyak Ekaterina

8 correct answers out of 11

29.11.2011

Sityaeva Alena

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

29.11.2011

Sityaeva Alena

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

29.11.2011

Bartashova 9G

9 correct answers out of 11

29.11.2011

Petrovskaya Zhenya 9A

7 correct answers out of 11
Your level of knowledge on the topic is 72.73%

29.11.2011

Lobanova Anastasia 9y

9 correct answers out of 11
Your level of knowledge on the topic is 81.82%

29.11.2011

Glushkov

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

29.11.2011

Vavilkina Elya 9a

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

29.11.2011

STRONDA KATYA 9a
7 correct answers out of 11
Your level of knowledge on the topic is 63.64%

29.11.2011

Kotova Masha 9g

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

30.11.2011

Baldzhyan

9 correct answers out of 11
Your level of knowledge on the topic is 81.82%

30.11.2011

Gerasimenko Roman 9a

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

01.12.2011

Elvira Shimokhina 9y
8 correct answers out of 11
Your level of knowledge on the topic is 72.73%

01.12.2011

Yushkevich Artyom 11b
8 correct answers out of 11
Your level of knowledge on the topic is 72.73%

03.12.2011

Perevoznikov 11 A

9 correct answers out of 11
Your level of knowledge on the topic is 81.82%

07.12.2011

Marat Fazliakhmetov 9\"A\"

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

08.12.2011

Petrukhina Olga 9V

11 correct answers out of 11

08.12.2011

Kolesnik 9V

10 correct answers out of 11
Your level of knowledge on the topic is 90.9%

09.12.2011

Kolesnikov Victor 9V

11 correct answers out of 11
Your level of knowledge on the topic is 100%

10.12.2011

Skladan Margarita 9V

11 correct answers out of 11
Your level of knowledge on the topic is 100%

10.12.2011

Barkhatova Daria 9B

11 correct answers out of 11
Your level of knowledge on the topic is 100%

11.12.2011

Kondratyev Artyom

7 correct answers out of 11
Your level of knowledge on the topic is 63.64%

11.12.2011

Ageeva Natalya

9 correct answers out of 11
Your level of knowledge on the topic is 81.82%

11.12.2011

Klimova Yulia 9V

11 correct answers out of 11
Your level of knowledge on the topic is 100%

12.12.2011

Stepanov Stanislav 9B

8 correct answers out of 11
Your level of knowledge on the topic is 72.73%

15.12.2011

nostia 9b

10 correct answers out of 11
Your level of knowledge on the topic is 90.91%

26.12.2011

Shulga Vladimir 9 B

11 correct answers out of 11
Your level of knowledge on the topic is 100%

26.12.2011

Vorobovich Nikita 9B

11 correct answers out of 11
Your level of knowledge on the topic is 100%

09.01.2012

ehson

out of 11 10 correct learn

21.01.2012

Christy and Vicki

cool

12.03.2012

Dasha

Dasha 10 out of 11

25.03.2012

Ivan 1v

11 correct answers out of 11
Your level of knowledge on the topic is 100%

25.03.2012

Ivan 10 \"B\"

11 correct answers out of 11
Your level of knowledge on the topic is 100%

03.04.2012

Alina

1 correct answer out of 11
Your level of knowledge on the topic is 100% I'm in 4th grade

04.04.2012

haha

11 correct answers out of 11
Your level of knowledge on the topic is 100%

17.04.2012

nataffka

10 correct answers out of 11
Your level of knowledge on the topic is 90.91%

30.04.2012

8 correct answers out of 11
Your level of knowledge on the topic is 72.73%

24.05.2012

Alyona

7 correct answers out of 11
Your level of knowledge on the topic is 63.64%

08.08.2013

Elina Udinka Avanesyan

7 out of 11

23.08.2013

hahaha

18.18

05.12.2013

idiot

2 of 11

10.10.2014

dark...

3 out of 11, I’ll probably be a janitor((

29.01.2017

Polka

5 of 11

12.02.2018

Shura

6 correct answers out of 11
Your level of knowledge on the topic is 54.55%

Exercise 1. Choose the correct answer.

1. The purity of gametes is determined:

• a) haploid set of chromosomes;
• b) absence of mutant genes;
• c) the presence of one of two allelic genes in the gamete;
• d) homozygosity

2. The reason for the uniformity of the first generation hybrids is:

• a) identical genotypes of the parents;
• b) heterozygosity of the parents;
• c) c) purity of the original parental individuals;
• d) incomplete dominance

3. When crossing two monoheterozygotes ( Ahh) there is a splitting according to the phenotype, corresponding to the formula:

• a) 1:1;
• b) 1:2;
• c) 3: 1;
• d) 9:7.

4. What does the offspring inherit from their parents:

• a) signs;
• b) properties;
• c) genotype;
• d) genes

5.What does the term “allele” mean:

• a) hereditary trait;
• b) locus;
• c) one of the possible states of the gene;
• d) mutant gene

6.What is the name of the phenomenon of pairing of signs:

• a) reciprocity;
• b) alternative;
• c) complementarity;
• d) allelism

7. How many alleles of one gene do descendants normally receive from each parent:

• a) two;
• b) several;
• into one;
• d) a lot

8. How many types of gametes are formed by an individual having a genotype that is homozygous for ten genes:

• a) two;
• b) several;
• into one;
• d) a lot

9. In what case do organisms with different genotypes have the same phenotype:

• a) with complete dominance;
• b) cannot have;
• c) with incomplete dominance;
• d) with lethality of one gene

10. How can we explain that individuals with the same genotype have different phenotypes:

• a) incomplete dominance;
• b) codominance;
• c) penetrance;
• d) complete dominance

11.What is the name of crossing parental individuals in different combinations(♀P 1 x ♂P 2; ♀P 2 x ♂P 1):

• a) backcross;
• b) analyzing;
• c) reciprocal;
• d) the opposite

12.What determines the number of gametes that an individual produces:

• a) diploidity;
• b) the number of dominant genes in the genotype;
• c) degree of heterozygosity;
• d) the number of recessive genes in the genotype

13.What is a phenotypic radical:

• a) a set of dominant genes;
• b) genes that determine the phenotype;
• c) genes obtained by F 1 hybrids;
• d) a set of recessive genes

14.Which generation corresponds to phenotypic splitting in the ratio 1: 2: 1:

• a) F 2 complete dominance;
• b) F 2 incomplete dominance;
• c) analytical crossing;
• d) F 1 incomplete dominance

15.Which genotypes appear with the same frequency in F 2 monohybrid crosses:

• and all;
• b) AA And Ahh;
• V) Ahh And ahh;
• G) AA And ahh

16. How is the independence of inheritance of characters established during hybridological analysis:

• a) by the number of splitting units;
• b) by the absence of recombinants;
• c) by the presence of recombinants;
• d) according to the splitting formula

17. Do certain genotypes arise in F 2 dihybrid crosses with a constant frequency:

• a) no;
• b) depending on F 1;
• c) often;
• d) always

Task 2. Solve the following problems.

1. Two normal parents gave birth to an albino child. Does a dominant or recessive gene determine albinism? Can this couple have normal children in the future?

2. One form of schizophrenia is inherited as a monogenic autosomal recessive trait. What is the probability of the disease manifesting itself in the offspring of two healthy parents if the paternal grandmother and maternal grandfather suffered from schizophrenia?

3. The son has blue eyes, the daughter brown. What color are the parents' eyes if both the grandparents on the mother's side are blue-eyed?

4. In one of the zoos in India, an albino tiger cub was born to a pair of tigers with normal coloring. Albino tigers are extremely rare. What crossbreeding should breeders carry out in order to get maximum amount albinos?

5. In a plant night beauty the red color of flowers is incompletely dominant over white, and therefore heterozygous individuals have pink flowers. In which type of crossing will all offspring have pink flowers? What color will dominate in the offspring of crossing plants with pink flowers?

6. A person has brown eyes (gene IN) dominate blues (gene b), and the ability to better master right hand(gene R) over left-handedness (gene r). What kind of offspring can be expected from the marriage of a blue-eyed right-hander and a brown-eyed left-hander if both are heterozygous for dominant traits?

7. In dogs, short hair dominates over long hair, black color over brown. What kind of offspring should be expected from crossing two animals: a female heterozygous for both genes and a brown male heterozygous for the gene for hair length? Use the law of probability.

8. Snapdragons have a gene for red flower color ( R) is incompletely dominant over the white gene ( r), so heterozygotes ( Rr) have pink flowers; broad leaf gene ( B) is incompletely dominant over the gene for narrow ( b), and therefore in heterozygotes ( Bb) leaves have an intermediate width. What will be the color of flowers and the width of leaves in F 2 from crossing a plant homozygous for dominant genes with a homozygous recessive?

9. In humans, left-handedness and albinism are determined by recessive autosomal genes localized on different chromosomes. Can parents have a normal phenotype if one child has inherited left-handedness and the other has albinism?

10. Brown eye color, dark hair color and right-handedness are dominant autosomal traits that are inherited independently. A blue-eyed, fair-haired, right-handed woman has a husband, a brown-eyed, dark-haired, left-handed man. They have a son - blue-eyed, blond-haired, left-handed and a daughter - brown-eyed, dark-haired, right-handed. Determine the genotypes of all family members.

11. Tomatoes have red colored fruits ( R) dominates yellow ( r), high growth ( T) over dwarf ( t), bilocular fruits ( D) over multi-nest ( d). A plant homozygous for all three dominant genes was crossed with a homozygous recessive. Which part of F 2 will be similar in appearance to the dominant parent? (Use the law of probability.)

Task 3. Fill in the blanks in the following statements.

1.For crossing, Mendel took different varieties peas with... signs.

2. One of the main conditions of the hybridological method is the use of... individuals as parents.

3. First generation hybrids inherit the trait... of the parent.

4. For all pairs of traits whose inheritance Mendel studied, in F 2 there was a split in the ratio... .

5. By “purity of gametes” Mendel understood the presence in them of only one of a pair of... genes.

6. Crossing using the same form first as a female parent and then as a male is called... .

7. To determine the genotype of a particular hybrid, Mendel carried out... crossing.

8. When analyzing the results of dihybrid crossing, in addition to the I and II laws, Mendel formulated the law... .

9. Backcrossing of a hybrid with the parent form is called....

10. The cytological basis of Mendel’s III law is... genes on different chromosomes.

11. The set of genes that determine the phenotype is called phenotypic... .

12. The appearance of individuals in F 2 with new phenotypes different from the parents is the result of... genes.

13. With incomplete dominance among the hybrid offspring, individuals with... a trait predominate.

14. If in a heterozygous state both allelic genes fully exhibit their effect, then this phenomenon is called....

Task 4. Indicate which of the following statements are correct.

1. The basis for the uniformity of the first generation hybrids is the homozygosity of the parental forms.

2. The number of gametes that an individual produces depends on the number of dominant genes.

3. In case of incomplete dominance, splitting by phenotype does not coincide with splitting by genotype.

4.Mendel's laws are universal.

5. Mendel’s laws apply only in the case of sexual reproduction of individuals.

6. The distribution of genotypes in the second generation of di- and polyhybrid crosses is random.

7. As a result of incomplete dominance, an intermediate trait develops in the hybrid.

8. Genes located on different chromosomes form new combinations as a result of the random divergence of chromosomes to the poles in meiosis.

9.Only two pairs of traits can be inherited independently.

10. The number of phenotypes in hybrid offspring is determined by the number of chromosomes in the parents.

Control questions

1. On what object were Mendel’s laws discovered?

2.Why should pure material be used in hybridological analysis?

3.Which type of dominance is more convenient for genetic analysis (complete or incomplete dominance)?

4.What are hybrids with new combinations of parental characteristics called?

5.On the basis of what law are the formulas for calculating segregation in polyhybrid crosses derived?

6. Why was Mendel unable to obtain the same results as on peas when working with hawkweed?

7.What are the conditions for the operation of Mendel’s laws?

8.What determines the independence of inheritance of traits?

9.What is the purpose of the Punnett grid?

10.How many pairs of traits can be inherited independently at the same time?

11.What is the mechanism of gene recombination during independent inheritance?

12.How do allelic genes behave in the case of codominance?

13.For what purpose is analytical crossing carried out?

14.What is gene expressivity and penetrance?

When preparing for the biology exam, the following book materials will also be useful:

Test on the topic “H. Mendel’s Laws” - 1 option
Part 1

1. How many alternative traits are taken into account in a monohybrid cross?
a) one b) two c) three
d) four e) more than four
2.What signs do the first generation hybrid exhibit?

3.What signs are paired?
a) red corolla and white seed
b) smooth and wrinkled surface
V) yellow and smooth surface of the seed
4.How are allelic genes distributed during meiosis?
a) appear in one gamete
b) end up in different gametes
5.How do genes for paired traits appear in a zygote?
a) are made up of parental gametes
c) unite randomly
b) are inherited

9: 3: 3: 1




7. Segregation by genotype during monohybrid crossing with incomplete dominance follows the formula:

8. If the producer has a heterozygous genotype, then during testing crossing the phenotypic cleavage in the descendants of the first generation will correspond to the formula
Part 2
9. Answer the given question, choose three correct answers
On what grounds did G. Mendel choose peas as the object of his research?
a) cross-pollinating d) perennial
b) self-pollinating e) contrasting characters
c) annual e) smoothed characteristics
Number Name Wording
1
law A.
splitting of characters A. “When two descendants (or self-pollination) of the first generation are crossed with each other (two heterozygous individuals) in the second generation, a split of characters is observed in a certain numerical ratio according to the genotype 1: 2: 1, according to the phenotype 3: 1”
2
law B.
independent inheritance of traits B. “When crossing two organisms belonging to different pure lines (two homozygous organisms), differing in one pair of alternative traits, all hybrids of the first generation (F1) will be uniform and will carry the dominant trait of one of the parents
3
law V.
uniformity B. “When crossing two homozygous organisms that differ from each other in two or more pairs of alternative traits, genes and their corresponding traits are inherited independently of each other and are combined in all possible combinations”
Answer to the question
1 2 3
Part 3

12.The color of the hair of guinea pigs depends on the content of the dark pigment melanin. White pigs (albinos) produce white offspring when crossed with each other. Dark pigs, when crossed with each other, produce dark offspring. Albino and dark hybrids have an intermediate (dark) color. What kind of offspring will be produced by crossing a semi-dark pig with a white one?
12. In humans, some forms of myopia dominate over normal vision, and the color of brown eyes dominates over blue. The genes for both pairs of traits are located on different chromosomes. What kind of offspring can be expected from the marriage of a heterozygous man with a woman with blue eyes and normal vision.
Work results:
“5” - 23 – 20 points
“4” - 19 – 16 points
“3” - 15 – 11 points
“2” - 10 points or less
Test on the topic “H. Mendel’s Laws” - option 2
Part 1
Answer the questions provided and choose one correct answer.
1. How many alternative traits are taken into account during dihybrid crossing?
a) one b) two c) three
d) four e) more than four
2.What signs appear in hybrids = 2 \* ROMAN II generation when the characters are split?
a) dominant b) recessive
3.What method of pollination did G. Mendel use to obtain hybrids = 2 \* ROMAN II generation?
a) cross
b) self-pollination
c) artificial pollination
4.What signs are paired?
a) polled (hornless) and horned cows
c) lumpiness and red color
b) black coat color and long hair
5.Where are the genes for paired traits located in a dihybrid cross?
a) one chromosome b) different chromosomes
6. In what kind of crossing does the phenotypic cleavage occur according to the formula
1: 2: 1
a) monohybrid with complete dominance
b) monohybrid with incomplete dominance
c) dihybrid with complete dominance
d) dihybrid with incomplete dominance
7. Segregation by genotype in a monohybrid cross with complete dominance follows the formula:
a) 9: 3: 3: 1 b) 1: 1 c) 3: 1 d) 1: 2: 1
8. If the producer has a homozygous dominant genotype, then during an analyzing cross the phenotypic cleavage in the descendants of the first generation will correspond to the formula
a) 3: 1 b) 1: 1 c) splitting will not occur
Part 2
Answer the questions provided, choose three correct answers
1. On what grounds did G. Mendel choose peas as the object of his research?
a) smoothed trait d) annual
b) contrasting characters e) self-pollinating
c) perennial e) cross-pollinating
10. Establish a correspondence between the number, name and wording of the genetic laws established by G. Mendel.
Number Name Wording
1
law A.
independent inheritance of traits A. “When crossing two organisms belonging to different pure lines (two homozygous organisms), differing in one pair of alternative traits, all hybrids of the first generation (F1) will be uniform and will carry the dominant trait of one of the parents
2
law B.
splitting
signs
B. “When crossing two homozygous organisms that differ from each other in two or more pairs of alternative traits, genes and their corresponding traits are inherited independently of each other and are combined in all possible combinations”
3
law V.
uniformity B. “When two descendants (or self-pollination) of the 1st generation are crossed with each other (two heterozygous individuals), in the 2nd generation a splitting of characters is observed in a certain numerical ratio according to the genotype 1: 2: 1, according to the phenotype 3: 1”
Answer to the question
1 2 3
Part 3
Solve the problems, pay attention to the correct format
11. As a result of crossing strawberry varieties with red fruits and white fruits, plants with pink berries are obtained in the offspring. what kind of offspring will be obtained from crossing hybrid strawberry plants with pink berries. (3 POINTS)
12. In dogs, black coat color dominates over coffee color, and short hair dominates over long hair. Both gene sets are located on different chromosomes. What percentage of black shorthair puppies can be expected from crossing two individuals heterozygous for both traits? (3 POINTS)
Work results:
“5” - 23 – 20 points
“4” - 19 – 16 points
“3” - 15 – 11 points
“2” - 10 points or less