Heredity and variability are properties of organisms. Genetics as a science

Heredity- the ability of organisms to transmit their characteristics and features of development to offspring.
Variability- a variety of characters among representatives of this species, as well as the property of offspring to acquire differences from parental forms.
Genetics- the science of the laws of heredity and variability.

2. Describe the contribution of scientists known to you to the development of genetics as a science by filling out the table.

History of the development of genetics

3. What methods of genetics as a science do you know?
The main method of genetics is hybridological. This is the crossing of certain organisms and the analysis of their offspring. This method was used by G. Mendel.
Genealogical - the study of pedigrees. Allows you to determine the patterns of inheritance of traits.
Twin - comparison of identical twins, allows you to study modification variability (determine the impact of the genotype and environment on the development of the child).
Cytogenetic - the study under a microscope of the chromosome set - the number of chromosomes, the features of their structure. Allows detection of chromosomal diseases.

4. What is the essence of the hybridological method for studying the inheritance of traits?
The hybridological method is one of the methods of genetics, a method of studying the hereditary properties of an organism by crossing it with a related form and then analyzing the characteristics of the offspring.

5. Why can peas be considered a successful object of genetic research?
Pea species differ from each other in a small number of well-distinguishable characters. Peas are easy to grow, in the Czech Republic it breeds several times a year. In addition, in nature, peas are self-pollinators, but in the experiment, self-pollination is easily prevented, and the researcher can easily pollinate a plant with one pollen from another plant.

6. Inheritance of what pairs of traits in peas was studied by G. Mendel?
Mendel used 22 pure pea lines. The plants of these lines had strongly pronounced differences from each other: the shape of the seeds (round - wrinkled); color of seeds (yellow - green); bean shape (smooth - wrinkled); arrangement of flowers on the stem (axillary - apical); plant height (normal - dwarf).

7. What is meant in genetics by a clean line?
A pure line in genetics is a group of organisms that have some characteristics that are completely transmitted to offspring due to the genetic homogeneity of all individuals.

Patterns of inheritance. monohybrid cross

1. Give definitions of concepts.
allelic genes- genes responsible for the manifestation of one trait.
Homozygous organism An organism that contains two identical allelic genes.
heterozygous organism An organism that contains two different allelic genes.

2. What is meant by monohybrid crossing?
Monohybrid crossing - crossing forms that differ from each other in one pair of alternative traits.

3. Formulate the uniformity rule for hybrids of the first generation.
When crossing two homozygous organisms that differ from each other in one trait, all hybrids of the first generation will have the trait of one of the parents, and the generation for this trait will be uniform.

4. Formulate a splitting rule.
When two descendants (hybrids) of the first generation are crossed with each other in the second generation, splitting is observed and individuals with recessive traits appear again; these individuals make up ¼ of the total number of descendants of the first generation.

5. Formulate the law of purity of gametes.
When formed, only one of the two “elements of heredity” responsible for this trait falls into each of them.

6. Using generally accepted conventions, draw up a monohybrid crossing scheme.

Describe the cytological foundations of monohybrid crossing using this example.
P is the parental generation, F1 is the first generation of offspring, F2 is the second generation of offspring, A is the gene responsible for the dominant trait, and the gene responsible for the recessive trait.
As a result of meiosis, in the gametes of the parent individuals, there will be one gene responsible for the inheritance of a certain trait (A or a). In the first generation, somatic cells will be heterozygous (Aa), so half of the gametes of the first generation will contain the A gene, and the other half will contain the a gene. As a result of random combinations of gametes in the second generation, the following combinations will arise: AA, Aa, aA, aa. Individuals with the first three combinations of genes will have the same phenotype (due to the presence of a dominant gene), and with the fourth - a different (recessive).

7. Solve the genetic problem for monohybrid crossing.
Task 1.
In watermelon, the green color of the fruit dominates over the striped. From the crossing of a green-fruited variety with a striped-fruited one, hybrids of the first generation were obtained, having fruits of a green color. The hybrids were pollinated and received 172 hybrids of the second generation. 1) How many types of gametes does a green-fruited plant form? 2) How many F2 plants will be heterozygous? 3) How many different genotypes will there be in F2? 4) How many plants with striped fruit will be in F2? 5) How many homozygous plants with green fruits will be in F2?
Solution
A - green color, a - striped color.
Since when plants with green and striped fruits were crossed, plants with a green fruit were obtained, it can be concluded that the parental individuals were homozygous (AA and aa) (according to Mendel's rule of uniformity of hybrids of the first generation of Mendel).
Let's make a crossover scheme.

Answers:
1. 1 or 2 (in case of heterozygote)
2. 86
3. 3
4. 43
5. 43.

Task 2.
Long hair in cats is recessive to short hair. A longhair cat crossed with a heterozygous shorthair cat produced 8 kittens. 1) How many types of gametes does a cat have? 2) How many types of gametes are formed in a cat? 3) How many phenotypically different kittens are in the litter? 4) How many genotypically different kittens are in the litter? 5) How many kittens are in the litter with long hair?
Solution
A is short hair and a is long hair. Since the cat had long hair, it is homozygous, its genotype is aa. The cat has the Aa genotype (heterozygous, short hair).
Let's make a crossover scheme.

Answers:
1. 2
2. 1
3. 4 long and 4 short
4. 4 with the Aa genotype, and 4 with the aa genotype
5. 4.

multiple alleles. Analyzing cross

1. Give definitions of concepts.
Phenotype- the totality of all signs and properties of the organism, which are revealed in the process of individual development under given conditions and are the result of the interaction of the genotype with a complex of factors of the internal and external environment.
Genotype- This is the totality of all the genes of an organism, which are its hereditary basis.

2. Why are the concepts of dominant and recessive genes relative?
A gene for a trait may have other "conditions" that are neither dominant nor recessive. This phenomenon can occur as a result of mutations and is called "multiple allelism".

3. What is meant by multiple allelism?

Multiple allelism is the existence of more than two alleles of a given gene in a population.

4. Fill in the table.

Types of interaction of allelic genes

5. What is analyzing cross and what is its practical significance?
Analyzing crosses are used to establish the genotype of individuals that do not differ in phenotype. In this case, the individual whose genotype needs to be established is crossed with an individual homozygous for the recessive gene (aa).

6. Solve the problem of analyzing crossover.
A task.

The white color of the corolla in phlox dominates over pink. A plant with a white corolla is crossed with a plant with a pink color. 96 hybrid plants were obtained, of which 51 are white and 45 are pink. 1) What are the genotypes of the parent plants? 2) How many types of gametes can a plant with a white corolla color form? 3) How many types of gametes can a plant with a pink corolla color form? 4) What phenotype ratio can be expected in the F2 generation from crossing F1 hybrid plants with white flowers?
Solution.
A - white color, a - pink color. The genotype of one plant A .. is white, the second aa is pink.
Since splitting 1:1 (51:45) is observed in the first generation, the genotype of the first plant is Aa.
Let's make a crossover scheme.

Answers:
1. Aa and aa.
2. 2
3. 1
4. 3 with white corolla: 1 with pink corolla.

Dihybrid cross

1. Give definitions of concepts.
Dihybrid cross- crossing individuals, which take into account differences from each other in two ways.
Punnett lattice is a table proposed by the English geneticist Reginald Punnett as a tool that is a graphical record for determining the compatibility of alleles from parental genotypes.

2. What ratio of phenotypes is obtained by dihybrid crossing of diheterozygotes? Illustrate your answer by drawing a Punnett lattice.
A - Yellow color of seeds
a - Green color of seeds
B - Smooth seed shape
c - Wrinkled form of seeds.
Yellow smooth (AABB) × Green wrinkled (AABB) =
P: AaBv×AaBb (diheterozygotes)
Gametes: AB, Av, aB, av.
F1 in the table:

Answer: 9 (yellow smooth): 3 (green smooth): 3 (yellow wrinkled): 1 (green wrinkled).

3. Formulate the law of independent inheritance of traits.
In a dihybrid cross, the genes and traits for which these genes are responsible are inherited independently of each other.

4. Solve genetic problems for dihybrid crossing.
Task 1.

Black color in cats dominates over fawn, and short hair dominates over long. Crossed purebred Persian cats (black longhair) with Siamese (fawn shorthair). The resulting hybrids were crossed with each other. What is the probability of getting a purebred Siamese kitten in F2; a kitten phenotypically similar to a Persian; long-haired fawn kitten (express in parts)?
Solution:
A - black color, and - fawn.
B - short hair, c - long.

Let's create a Punnett lattice.

Answer:
1) 1/16
2) 3/16
3) 1/16.

Task 2.

In tomatoes, the round shape of the fruit dominates over the pear-shaped, and the red color of the fruit dominates over the yellow. 120 plants were obtained from crossing a heterozygous plant with a red color and a pear-shaped fruit and a yellow-fruited plant with rounded fruits. 1) How many types of gametes does a heterozygous plant with a red color of fruits and a pear-shaped form form? 2) How many different phenotypes are obtained from such crossing? 3) How many different genotypes were obtained from such a crossing? 4) How many plants turned out with a red color and a rounded shape of the fruit? 5) How many plants turned out with a yellow color and a rounded shape of the fruit?
Solution
A - rounded shape, a - pear-shaped.
B - red color, c - yellow color.
We determine the genotypes of the parents, the types of gametes and write down the crossing scheme.

Let's create a Punnett lattice.

Answer:
1. 2
2. 4
3. 4
4. 30
5. 30.

Chromosomal theory of heredity. Modern ideas about the gene and genome

1. Give definitions of concepts.
Crossing over- the process of exchanging sections of homologous chromosomes during conjugation in prophase I of meiosis.
Chromosomal map- this is a diagram of the mutual arrangement and relative distances between the genes of certain chromosomes that are in the same linkage group.

2. In what case does the violation of the law of independent inheritance of traits occur?
When crossing over, Morgan's law is violated, and the genes of one chromosome are not inherited linked, since some of them are replaced by allelic genes of the homologous chromosome.

3. Write the main provisions of T. Morgan's chromosome theory of heredity.
A gene is a section of a chromosome.
Allelic genes (genes responsible for one trait) are located in strictly defined places (loci) of homologous chromosomes.
Genes are arranged linearly on chromosomes, that is, one after another.
In the process of gamete formation, conjugation occurs between homologous chromosomes, as a result of which they can exchange allelic genes, that is, crossing over can occur.

4. Formulate Morgan's law.
Genes located on the same chromosome during meiosis fall into the same gamete, that is, they are inherited linked.

5. What determines the probability of divergence of two non-allelic genes during crossing over?
The probability of divergence of two non-allelic genes during crossing over depends on the distance between them in the chromosome.

6. What underlies the compilation of genetic maps of organisms?
Calculating the frequency of crossing over between any two genes of the same chromosome responsible for different traits makes it possible to accurately determine the distance between these genes, and hence start building a genetic map, which is a diagram of the mutual arrangement of genes that make up one chromosome.

7. What are chromosome maps for?
With the help of genetic maps, you can find out the location of animal and plant genes and information from them. This will help in the fight against various incurable diseases.

Hereditary and non-hereditary variability

1. Give definitions of concepts.

reaction rate- the ability of the genotype to form in ontogenesis, depending on environmental conditions, different phenotypes. It characterizes the share of participation of the environment in the implementation of the trait and determines the modification variability of the species.
Mutation- persistent (that is, one that can be inherited by the descendants of a given cell or organism) transformation of the genotype that occurs under the influence of the external or internal environment.
2. Fill in the table.

3. What determines the limits of modification variability?
The limits of modification variability depend on the rate of reaction, which is genetically determined and inherited.

4. What do combinative and mutational variability have in common and how do they differ?
General: both types of variability are due to changes in the genetic material.
Differences: combinative variability occurs due to the recombination of genes during the fusion of gametes, and mutational variability is caused by the action of mutagens on the body.

5. Fill in the table.

Types of mutations

6. What is meant by mutagenic factors? Give relevant examples.
Mutagenic factors - influences leading to the occurrence of mutations.
These can be physical effects: ionizing radiation and ultraviolet radiation that damages DNA molecules; chemicals that disrupt DNA structures and replication processes; viruses that insert their genes into the DNA of the host cell.

Inheritance of traits in humans. Hereditary diseases in humans

1. Give definitions of concepts.
Genetic diseases- diseases caused by gene or chromosomal mutations.
Chromosomal diseases- diseases caused by a change in the number of chromosomes or their structure.

2. Fill in the table.

Inheritance of traits in humans

3. What is meant by sex-linked inheritance?
Sex-linked inheritance is the inheritance of traits whose genes are located on the sex chromosomes.

4. What traits are sex-linked in humans?
Sex-linked hemophilia and color blindness are inherited in humans.

5. Solve genetic problems for the inheritance of traits in humans, including sex-linked inheritance.
Task 1.

In humans, the gene for long eyelashes is dominant over the gene for short eyelashes. A woman with long eyelashes, whose father had short eyelashes, married men with short eyelashes. 1) How many types of gametes are formed in a woman? 2) How many types of gametes are formed in men? 3) What is the probability of the birth of a child with long eyelashes in this family (in %)? 4) How many different genotypes and how many phenotypes can be among the children of this married couple?
Solution
A - long eyelashes
a - short eyelashes.
The female is heterozygous (Aa) because her father had short eyelashes.
The male is homozygous (aa).

Answer:
1. 2
2. 1
3. 50
4. 2 genotypes (Aa) and 2 phenotypes (long and short eyelashes).

Task 2.

In humans, a free earlobe dominates over a closed one, and a smooth chin is recessive to a chin with a triangular fossa. These traits are inherited independently. From the marriage of a man with a closed earlobe and a triangular fossa on his chin and a woman with a free earlobe and a smooth chin, a son was born with a smooth chin and a closed earlobe. What is the probability of the birth in this family of a child with a smooth chin and free earlobe; with a triangular fossa on the chin (in %)?
Solution
A - free earlobe
a - not free earlobe
B - triangular fossa
c - smooth chin.
Since the couple had a child with homozygous traits (aavb), the genotype of the mother is Aavb, and the father is aaBv.
Let's write down the genotypes of the parents, the types of gametes and the crossing scheme.

Let's create a Punnett lattice.

Answer:
1. 25
2. 50.

Task 3.

In humans, the gene that causes hemophilia is recessive and is located on the X chromosome, while albinism is caused by an autosomal recessive gene. Parents, normal in these characteristics, had a son with an albino and a hemophiliac. 1) What is the probability that their next son will show these two abnormal features? 2) What is the probability of having healthy daughters?
Solution:
X° - the presence of hemophilia (recessive), X - the absence of hemophilia.
A - normal skin color
a is an albino.
Parents' genotypes:
Mother - Х°ХАа
Father - HUAA.
Let's create a Punnett lattice.

Answer: the probability of manifestation of signs of albinism and hemophilia (genotype X ° Uaa) - in the next son - 6.25%. The probability of the birth of healthy daughters - (XXAA genotype) - 6.25%.

Task 4.

Hypertension in humans is determined by a dominant autosomal gene, while optic atrophy is caused by a sex-linked recessive gene. A woman with optic atrophy married a man with hypertension whose father also had hypertension and whose mother was healthy. 1) What is the probability that a child in this family will suffer from both anomalies (in %)? 2) What is the probability of having a healthy baby (in %)?
Solution.
X° - the presence of atrophy (recessive), X - the absence of atrophy.
A - hypertension
a - no hypertension.
Parents' genotypes:
Mother - X ° X ° aa (as she is ill with atrophy and without hypertension)
Father - XUAa (since he is not sick with atrophy and his father was with hypertension, and his mother is healthy).
Let's create a Punnett lattice.

Answer:
1. 25
2. 0 (only 25% of daughters will not have these deficiencies, but they will be carriers of atrophy and without hypertension).

genotypically homogeneous offspring obtained initially from one self-pollinating or self-fertilizing individual through selection and further self-pollination (self-fertilization). The term was introduced in 1903 by W. Johansen. Since self-pollination (self-fertilization) is the highest degree of inbreeding, Ch. l. is a group of organisms that are homozygous for most genes. Johansen's work on the inheritance of traits in Ch. l. led to the important conclusion about the inefficiency of selection within Ch. l., i.e., that the source material for selection must be genotypically heterogeneous. The fact that the descendants of individuals differing in phenotype from one Ch. l. characterized by the same degree of phenotypic. variability, led to the formation of the concept of the "reaction rate", i.e., the possible range of variability of signs caused by external. conditions in organisms of the same genotype. Sometimes Ch. l. called lines obtained by inbreeding to a lesser degree (the so-called inbred lines, for example, "Ch. l ....

Clean line

Specialist. offspring without crossing. F 1, 280.

Clean line

genotypically homogeneous offspring of constantly self-pollinating plants or self-fertilizing animals, most of whose genes are in the homozygous state. The term was introduced in 1903 by the Danish geneticist W. Johansen, who, in experiments on leguminous plants, proved that in C. l. under the same conditions, a similar phenotype appears. Ch. l. are derived from a single ancestor and maintained through forced self-pollination and selection. Individuals in Ch. l. reproduce in a number of generations the same hereditarily fixed traits. Ch. l. are important in page - x. production, being the main structural elements of plant varieties. Hybridization of two H. l. in some cases leads to the effect of heterosis in the first hybrid generation (this is how some hybrid forms are obtained ...

CLEAN LINE

genotypically homogeneous offspring obtained initially from one self-pollinating (district) or self-fertilizing (female) individuals through selection and further self-pollination or self-fertilization. It is a group of organisms that are homozygous for most genes. The study of the inheritance of traits in human l. is an important method of experimental genetics. Ch. l. sometimes called. lines of laboratory well-nyh (eg, mice) obtained as a result of consanguinity. crosses.