Fundamentals of the doctrine of heredity and variability

Option I

Exercise 1.

1. The ability of organisms to acquire new characteristics in the process of life is called:

2. Somatic cells in most animals, higher plants and humans are

3. The set of chromosomes in human somatic cells is:

a) 48 b) 46 c) 44 d) 23

4. Individuals in whose offspring NOT splitting of the trait is detected, they are called:

a) hybrid b) homozygous c) heterozygous d) hemizygous

5. The trait that manifests itself in the hybrid generation is called:

a) dominant b) recessive c) hybrid d) mutant

6. A phenotype is a combination of:

a) Recessive genes b) Dominant genes

c) Externally manifested traits d) Genotypes of the same species

7. Gene:

a) Unit hereditary information b) Section of the I-RNA molecule

c) A piece of DNA d) Contains a certain set of nucleotides

8. Hybrids of the 1st generation with monohybrid crossing of homozygous individuals

a) Uniform

b) Detect phenotype cleavage - 1: 3: 1

c) Detect phenotype cleavage - 1: 1

d) Phenotypic cleavage is detected - 1: 2: 1

9. Mendel's second law:

a) Describes dihybrid crossing

b) Fair when crossing two heterozygotes with each other

c) Claims that when heterozygotes are crossed with each other, a splitting of 3: 1 according to the phenotype is observed

10. Dihybrid crossing:

a) this is a crossing for two pairs of allelic genes

b) fundamentally different from monohybrid crossing

c) made it possible to identify the recombination of signs

d) underlies the third Mendel's law

11. When crossing individuals with genotypes aa and Aa, splitting is observed in the offspring according to

phenotype in relation to

12. Paired genes located in homologous chromosomes and determining color

pea flowers are called

a) linked b) recessive c) dominant d) allelic

13. An individual with the AABb genotype produces gametes:

a) AB, Av, aB, av b) AB, Av c) Av, aB d) Aa, Bb, AA, BB

14. The nucleus of the human egg cell contains 23 chromosomes, and in the nucleus of the male cell:

a) 24 b) 23 c) ​​46 d) 32

15. The chromosome set of female sex cells contains:

a) two XX - chromosomes b) 22 autosomes and one X - chromosome

c) 44 autosomes and one X - chromosome d) 44 autosomes and two X - chromosomes

16. Can a daughter get hemophilia if her father is hemophilic? :

a) maybe, because the hemophilia gene is located on the Y-chromosome

b) maybe, if the mother is a carrier of the hemophilia gene

c) cannot, because she is heterozygous for the X chromosome

d) cannot, if the mother is a carrier of the hemophilia gene

17. The boundaries of phenotypic variability are called:
a) Variation series b) Variation curve c) Reaction norm d) Modification
18. Rotation of the chromosome by 180 ° is called ...
a) Translocation b) Duplication c) Deletion d) Inversion

19. Variability that does not affect the genes of the organism and does not alter the hereditary

material is called ...
a) Genotypic variability b) Combinative variability
c) Mutational variability d) Phenotypic variability

20. Mutations that occur in the germ cells are called ...
a) Somatic b) Generative c) Useful d) Gene

21. Loss of four nucleotides in DNA is:

a) gene mutation; b) chromosomal mutation; c) genomic mutation.

22. The rate of reaction of the trait:

a) is inherited; b) depends on environment; c) is formed in ontogenesis.

Task 2.

1. Mutations as opposed to modifications:

a) inherited b) not inherited

c) arise by chance d) correspond to the influence of the external environment

e) arise under the influence of radiation e) are always dominant

2. Somatic mutations:

a) Manifested in organisms that have arisen; b) They are not inherited;

c) Manifested in offspring; d) They arise in the cells of the body;

e) Can be inherited; f) Occur in gametes.

Building 3.

Set correspondence:

Between the types of variability and their characteristics.

Characteristic: Variation type:

1. It is of a group nature. A) modification;
2. Wears individual character... B) mutational.
3. Inherited.
4. Not inherited.
5. It is due to the normal reaction of the body.
6. Inadequate to changes in environmental conditions.

Task 4.

Define right and wrong judgments:

1. Down syndrome is caused by a chromosomal mutation.

2. Gene and point mutations are synonymous.

3. Changes in traits caused by environmental factors are not inherited.

4. Mutations incompatible with life are called lethal.

5. Mutations in somatic cells are inherited.

6. The source of combinative variability is meiosis.

7. Polyploidy is caused by a chromosomal mutation.

8. Modification variability - a change in the genotype within the reaction norm.

9. The set of sex chromosomes of a male of any animal species is designated as XY.

10. The Y chromosome contains all genes allelic to the X chromosome genes.

11. Traits linked to the X chromosome appear in men regardless of their dominance or recessiveness.

12. A woman carrying the hemophilia gene has a 50% chance of passing this gene on to her children.

13. The son of a carrier has a 100% chance of developing hemophilia.

Verification test work

on this topic : Fundamentals of the doctrine of heredity and variability

Option number 2

1. Science that studies heredity and variability:

a) cytology b) selection c) genetics d) embryology

2. The ability of organisms to transmit their traits and genes from parents to offspring

called:

a) genetics b) variability c) selection d) heredity

3. Sex cells in most animals, humans are

a) Polyploid b) Diploid c) Haploid d) Tetraploid

4. A unit of hereditary information is:

a) Genotype b) Phenotype c) Gene d) Protein

5. Genotype:

a) The set of all genes of an individual b) The set of all characteristics of organisms

c) Always completely coincides with the phenotype d) Determines the limits of the normal reaction of the organism

6. Husband and wife have dimples in their cheeks, but their children do not. Dominant or recessive sign

the presence of dimples on the cheeks:

a) dominant b) recessive c) sex-linked d) linked

7. Individuals in the offspring of which splitting of the trait is found are called:

a) hybrid b) homozygous; c) heterozygous d) hemizygous

8. A sign that NOT manifests itself in the hybrid generation called:

a) dominant b) recessive c) intermediate d) mutant

9. What part of individuals with a recessive trait will appear in the first generation when crossing

two parents heterozygous for this trait?

a) 75% b) 50% c) 25% d) 0%

10. When crossing individuals with genotypes Aa and Aa (subject to complete dominance)

splitting is observed in the offspring according to the phenotype in the ratio

a) 1: 1 b) 3: 1 c) 9: 3: 3: 1 d) 1: 2: 1

11. Mendel's third law:

a) Describes monohybrid crossing

b) This is the law of independent inheritance of traits

c) Asserts that each pair of traits is inherited independently of the others

d) Claims that with a dihybrid crossing in F 2, a splitting according to the genotype 9: 3: 3: 1 is observed

12. Inheritance of traits determined, localized in sex chromosomes

called:

a) dihybrid b) linked c) monohybrid d) linked to the floor

13. Which chromosome will be decisive in determining the female sex in birds?

a) X-chromosome of sperm b) Y-chromosome of sperm

c) X-chromosome of the egg d) Y-chromosome of the egg

14. An individual with the AaBb genotype produces gametes:

a) AB, Av, aB, av b) AB, av c) Av, aB d) Aa, Bb, AA, BB

15. The chromosome set of male sex cells contains:

a) One X chromosome and one Y chromosome b) 22 autosomes and one X or Y chromosome

c) 44 autosomes and XY - chromosomes d) 44 autosomes, one X or Y - chromosomes

16. Mutations can be due to

a) a new combination of chromosomes as a result of gamete fusion

b) crossing of chromosomes during meiosis

c) new combinations of genes as a result of fertilization

d) changes in genes and chromosomes

17. The loss of a chromosome section is called ...
a) Deletion b) Duplication c) Inversion d) Translocation
18. Shereshevsky-Turner syndrome can result from ...
a) Polyploidy b) Polysomy c) Trisomy d) Monosomy

19. Indicate directional variability:
a) Combinative variability b) Mutational variability
c) Relative variability d) Modification variability
20. Crossing over is a mechanism ...
a) Combinative variability b) Mutational variability
c) Phenotypic variability d) Modification variability

21. Non-hereditary variability is called:

a) indefinite; b) certain; c) genotypic.

22. Polyploid organisms result from:

a) genomic mutations; b) gene mutations;

c) modification variability; d) combinative variability.

Task 2.

Choose three correct answers out of six.

1.Mutations are:

a) greening potato tubers in the light b) brachydactyly

c) Down syndrome d) bending of the trunk of a pine tree growing in a crack in the rock

e) the transformation of a tadpole into a frog f) the appearance of white eyes in Drosophila

2. The rate of reaction in organisms:

a) is determined by a set of genes;

b) different for different signs;

c) it exists for a short time and can change;

d) allows them to adapt to the conditions of existence;

e) the same for different signs of one organism;

f) is determined by environmental conditions.

Task 3.

Set correspondence:

Between the types of mutations and their characteristics.

Feature: Types of mutations:

1. The number of chromosomes increased by 1-2. A) genetic;
2. One DNA nucleotide is replaced by another. B) chromosomal;
3. A section of one chromosome has been transferred to another. C) genomic.
4. There was a loss of a portion of the chromosome.
5. The chromosome section is rotated 180 °.
6. There was a multiple increase in the number of chromosomes.

Task 4. Select incorrect statements.

1. Down syndrome is caused by a genomic mutation.
2. Gene and genomic mutations are synonymous.
3. Changes in traits caused by environmental factors are inherited.
4. Mutations that cause a decrease in viability are called semi-lethal.
5. Non-hereditary variability is a change in the phenotype within the normal range of the reaction.
6. Artificial mutagenesis is used to increase the number of mutations.
7. Mutations in germ cells are inherited.
8. The source of combinative variability is mitosis.
9. Genes that determine the development of different traits are called allelic.
10. The totality of the genes of an organism makes up its phenotype.
11. An example of an analyzing crossing is crossing Aa x aa.
12. Linkage groups of genes are found on different chromosomes.
13. Environmental conditions, as a rule, change the rate of reaction of the body.

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Answers.

Option 1

Exercise 1.

Task 2. 1) a, c, e; 2) a, b, d.

Task 3. A - 1.4.5; B - 2,3,6.

Allelic genes. So, we have established that heterozygous individuals have two genes in each cell - A and a responsible for the development of the same trait. Genes that determine the alternative development of the same trait and are located in identical regions of homologous chromosomes are called allelic genes or alleles. Any diploid organism, be it a plant, animal or human, contains in each cell two alleles of any gene. The exception is the sex cells - gametes. As a result of meiosis, the number of chromosomes in them decreases by 2 times, so each gamete has only one allelic gene. Alleles of one gene are located in one place of homologous chromosomes.

Schematically, a heterozygous individual is designated as follows:
Homozygous individuals with a similar designation look like this:
or, but they can be written as AA and aa.

Phenotype and genotype. Considering the results of self-pollination of F 2 hybrids, we found that plants grown from yellow seeds, being similar in appearance, or, as they say in such cases, having the same phenotype, have a different combination of genes, which is commonly called the genotype. Thus, the phenomenon of dominance leads to the fact that individuals with the same phenotype can have different genotypes. The concepts "genotype" and "phenotype" are very important in genetics. The totality of all genes of an organism makes up its genotype. The totality of all the characteristics of an organism, from external to the features of the structure and functioning of cells and organs, constitutes a phenotype. The phenotype is formed under the influence of the genotype and environmental conditions.

Analyzing crossing. By the phenotype of an individual, it is far from always possible to determine its genotype. In self-pollinating plants, the genotype can be determined in the next generation. For cross-breeding species, the so-called analysis cross is used. When analyzing crossing, an individual whose genotype should be determined is crossed with individuals homozygous for the recessive gene, that is, having the aa genotype. Let's consider an analyzing crossing using an example. Let individuals with genotypes AA and Aa have the same phenotype. Then, when crossed with an individual recessive for a determined trait and having a genotype aa, the following results are obtained:

It can be seen from these examples that individuals homozygous for the dominant gene do not split in F1, and heterozygous individuals, when crossed with a homozygous individual, give splitting already in F1.

Incomplete dominance. It is far from always that heterozygous organisms in phenotype exactly correspond to the parent, homozygous for the dominant gene. Often heterozygous offspring have an intermediate phenotype, in such cases they speak of incomplete dominance (Fig. 36). For example, when crossing a plant with a night beauty with white flowers (aa) with a plant with red flowers (AA), all F 1 hybrids have pink flowers (Aa). When hybrids with pink color of flowers are crossed among themselves in F 2, splitting occurs in a ratio of 1 (red): 2 (pink): 1 (white).

Rice. 36. Intermediate inheritance from the night beauty

The principle of gamete purity. In hybrids, as we know, different alleles are combined, introduced into the zygote by the parental gametes. It is important to note that different alleles found in one zygote and, therefore, in the organism that developed from it, do not affect each other. Therefore, the properties of alleles remain constant regardless of which zygote they have been in before. Each gamete always contains only one allele of a gene.

The cytological basis of the principle of gamete purity and the law of cleavage is that homologous chromosomes and allelic genes located in them are distributed in meiosis among different gametes, and then reunite in the zygote during fertilization. In the processes of divergence in gametes and association into zygotuallelic genes, they behave as independent, whole units.

1. Will it correct definition: a phenotype is a combination external signs organism?
2. What is the purpose of analyzing crossing?
3. What do you think practical significance have knowledge of genotype and phenotype?
4. Compare the types of inheritance of genetic traits during crosses with the behavior of chromosomes during meiosis and fertilization.
5. When gray and black mice were crossed, 30 offspring were obtained, of which 14 were black. It is known that gray color dominates over black. What is the genotype of the parental mice? See the end of the tutorial for the solution to the problem.
6. A blue-eyed man whose both parents had Brown eyes, married a brown-eyed woman whose father had brown eyes and whose mother blue. From this marriage, a blue-eyed son was born. Determine the genotypes of all the persons mentioned.

1) homozygous for a recessive trait

2) is homozygous for the dominant trait

3) heterozygous

4) forms two types of gametes

5) forms one type of gametes

6) clean line

6. An individual with the AA genotype:

1) is homozygous for a recessive trait;

2) is homozygous for the dominant trait;

3) heterozygous;

4) forms two types of gametes;

5) forms one type of gametes;

6) clean line;

7. Mendelian signs in humans include

2) blood pressure

3) a white strand of hair above the forehead

4) adherent earlobe

6) the ability to predominantly use the right hand

eight . Varieties of inter-allelic gene interaction:

1) codominance

2) epistasis

3) complementarity

4) complete domination.

5) polymerization

6) incomplete dominance

9. Match the genotypes of people with their blood types:

Genotypes: blood groups:

1) I A I O A. first blood group

2) I О I О B. second blood group

3) I A I A B. third blood group

4) I B I O G. fourth blood group

Part 3:

SITUATION TASKS

1. Determine the penetrance of the allele responsible for the manifestation of the trait, if 80 children were born-carriers of this gene, but phenotypically manifested itself in 30 offspring. a) 20% b) 75% c) 12% d) 10%

2. Can parents with achondroplasia (shortening of long bones, autosomal dominant trait) have a healthy child? If so, how likely?

a) yes, 25% b) yes, 50% c) yes, 75% d) no

3. A father with an MM blood group has a child with an MN blood group. What genotype can NOT be in the mother of the child?

a) NN b) MN c) MM

4. Below are the different combinations of parent and child blood group phenotypes. Which ones are actually impossible?

FATHER MOTHER CHILD

a) AB A0 B

ANSWER STANDARDS:

Part 1

Part 2

Part 3 1 - b 2 - c 3 - c 4 - c

Date ____________________

LABORATORY WORK No. 5

Topic: Regularities of the inheritance of traits in di - and polyhybrid crossing. Independent inheritance of traits. Interaction of non-allelic genes

Purpose of the lesson :

based on knowledge of the basic laws of Mendel and the forms of interaction of non-allelic genes, be able to predict the manifestation of traits in offspring.

Lesson objectives :

be able to solve problems on di- and polyhybrid crossing and on the interaction of non-allelic genes.

Tests to control the final level of knowledge (answer the questions suggested by the teacher).

OPTION NO.

1______ 6______

2______ 7______

3______ 8______

4______ 9______

5______ 10______

Number of points: _______

G. Mendel's laws apply to traits inherited monogenously with complete dominance. A genotype is a system of interacting genes. Interaction occurs between allelic and non-allelic genes localized on the same and different chromosomes. The gene system creates a balanced genotypic environment that influences the function and expression of each gene. As a result, a certain phenotype of the organism is formed, all the signs of which are strictly coordinated in time, place and strength of manifestation. Physicians should draw up genetic patterns of inheritance of mendelian and non-mendelian traits and calculate the likelihood of their manifestation in offspring.

Self-study questions:

1. The law of independent inheritance of traits.

2. Hybridological analysis for di- and polyhybrid crosses.

3. The conditions under which the third law of G. Mendel is observed and the characteristics are inherited independently.

4. Non-allelic genes: definition, designation, location

5. Types of interaction of non-allelic genes. Hybridological analysis of the interaction of non-allelic genes.

6. Give a definition of complementarity. What traits are complementary inherited in humans?

7. Justify the phenomenon of epistasis.

8. What types of epistasis exist?

9. Epistatic (suppressors, inhibitors) and hypostatic (suppressed) genes. What traits in humans are inherited as epistasis?

10. Explain the phenomenon of polymerization. What traits in humans are polymeric inherited?

11. Does the interaction between non-allelic genes violate the law of their independent inheritance?

12. Explain the mechanism of the "effect" of the position of genes, give examples of inheritance

signs in humans.

Basic terms

The gene pool of a population can be described either by gene frequencies or by genotype frequencies. Let's imagine that there are N diploid individuals in the population, differing in one pair of alleles (A and a); D - means the number of homozygotes for the dominant allele (AA); P is the number of homozygotes for the recessive allele (aa); H is the number of heterozygotes (Aa). Thus, in the population there will be three types of individuals with genotypes AA, Aa, and aa, respectively. Since each individual with the AA genotype has two alleles A, and each individual Aa has one allele A, total number alleles A will be 2D + H. Then p is the frequency of occurrence of the dominant allele A is equal to:

The frequency of the recessive allele (a) is usually denoted q. The sum of the frequencies of genes A and a is equal to one, p + q = 1, hence q = 1-p. If a gene is represented by only two alleles (A and a) with a frequency of p and q, then what will be the frequencies of the three possible genotypes?

The question posed is answered by the Hardy - Weinberg law. At first glance, it may seem that individuals with a dominant phenotype will occur more often than with a recessive one. However, the ratio of 3: 1 is observed only in the offspring of two individuals heterozygous for the same alleles. Mendel's laws say nothing about the frequencies of genotypes and phenotypes in populations. They are discussed in the named law. It was formulated independently by the mathematician J. Hardy in England and the physician Wilhelm Weinberg in Germany. To understand the meaning of this law, suppose that males and females in a population interbreed by chance, or, which is the same thing, the gametes of males and females will be combined randomly, forming zygotes. The zygote combines maternal and paternal chromosomes, each of the homologous chromosomes carries one allele from a given pair. The formation of individuals with the AA genotype is due to the probability of obtaining allele A from the mother and allele A from the father, i.e. pxp = p2.

Similarly, the emergence of the aa genotype, the frequency of occurrence of which is equal to q2. The Aa genotype can arise in two ways: the organism receives the A allele from the mother, the a allele from the father, or, conversely, the A allele from the father, and the a allele from the mother. The probability of both events is pq, and the total probability of genotype Aa occurrence is 2pq. Thus, the frequency of the three possible genotypes can be expressed by the equation: (p + q) 2 = p2 + 2pq + q2 = 1

It follows from the equation that if the crossing is random, then the frequencies of the genotypes are related to the frequencies of the alleles by simple ratios according to the Newton binomial formula.

Let us consider an example when the allele frequencies of a given gene in a population will be 0.1A; 0.3a (the geometric expression of the Hardy - Weinberg law for this case is shown in Fig. 21). In the offspring, per 100 zygotes, there will be 49 AA homozygotes, 9 aa homozygotes and 42 Aa heterozygotes, i.e. this corresponds to the already known ratio of genotypes - p2 (AA): 2pq (Ad): q2 (aa).

Interestingly, in the next generation, gametes with the A allele will arise with a frequency of 0.7 (0.49 from AA homozygotes + 0.21 from Aa heterozygotes). This ratio will continue in the future. The frequencies of genes, and therefore of genotypes, remain unchanged from generation to generation - this is one of the main provisions of the Hardy-Weinberg law. However, the named law is of a probabilistic nature and therefore is realized in an infinitely large population. In this case, the frequencies of genes remain unchanged if: there is unlimited panmixia; there is no natural selection; new mutations of the same genes do not arise; there is no migration of individuals with other genotypes from neighboring populations.