Molecular biology and genetics. Dictionary

Clean line- a group of organisms that have certain characteristics that are completely transmitted to offspring due to the genetic homogeneity of all individuals. In the case of a gene that has multiple alleles, all organisms belonging to the same pure lineage are homozygous for the same allele of that gene.

Pure lines are often called plant varieties that, when self-pollinated, produce genetically identical and morphologically similar offspring.

The analogue of a pure line in microorganisms is a strain.

Pure (inbred) lines in animals with cross-fertilization are obtained by inbreeding over several generations. As a result, animals that make up a pure line receive identical copies of the chromosomes of each of the homologous pairs.

Using clean lines in scientific research

The discoverer of the laws of heredity, Gregor Mendel, used pure lines of peas for crossing in his experiments. In 1903, geneticist V. Johansen showed the ineffectiveness of selection in pure lines, which played an important role in the development of evolutionary theory and selection practice.

Currently, pure lines of animals (primarily rats and mice) and plants play a vital role in biological and medical research. The genetic homogeneity of the organisms used by scientists increases the reproducibility of the results and reduces the likelihood of genetic differences between individuals (for example, in the control and experimental groups) influencing the results of the study. Using traditional breeding and genetic engineering methods, many pure lines with desired properties have been obtained (for example, an increased tendency to drink alcohol, high levels of

Clean line

Pure lines are often called plant varieties that, when self-pollinated, produce genetically identical and morphologically similar offspring.

The analogue of a pure line in microorganisms is a strain.

Pure (inbred) lines in cross-fertilized animals are obtained by inbreeding over several generations. As a result, animals that make up a pure line receive identical copies of the chromosomes of each of the homologous pairs.

Using clean lines in scientific research

Currently, pure lines of animals (primarily rats and mice) and plants play a vital role in biological and medical research. The genetic homogeneity of the organisms used by scientists increases the reproducibility of the results and reduces the likelihood of genetic differences between individuals (for example, in the control and experimental groups) influencing the results of the study. Using traditional breeding and genetic engineering methods, many pure lines with specified properties (for example, an increased tendency to drink alcohol, a high incidence of various forms of cancer, etc.) have been obtained and used for specific studies.

Use of pure (inbred) lines in breeding

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See what “Clean Line” is in other dictionaries:

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Nowadays, biotechnology and genetics are actively developing. In Russia, genetics and cybernetics suffered a disastrous fate at the end of the thirties of the last century. The “people's” academician Trofim Denisovich Lysenko, favored by the Soviet government, declared genetics “the corrupt girl of imperialism.” All developments were stopped, scientists involved in this science were repressed. After 1956, research was resumed. To obtain accurate experimental results for genetic experiments, genetically pure lines of animals and plants are needed. So what is a pure line in biology?

Basic concept of clean line

A pure line in genetics is a group of organisms that have certain characteristics that are completely transmitted to the offspring due to the genetic homogeneity of all individuals. (From the free encyclopedia).

This is the definition of a pure line in biology.

These organisms are homogeneous because their genetic code is identical. They come from one ancestor, or in plants they are obtained as a result of self-pollination.

Breeders were breeding pure lines long before the advent of genetics and the concept of a genetic code. For example, the famous line of Oryol trotters. Initially, they were all descendants of the famous Smetanka, Count Orlov’s trotter.

Using artificial selection, traits that were of interest were selected in the offspring. There are currently 11 pure trotter lines.

Pure lines of chickens with increased egg production and pure lines of cows, goats and other farm animals were also bred. What are clean lines and why do they matter to agriculture? This makes it possible to improve the required properties of animals, increase their numbers, and obtain products of the required quality.

Natural selection in pure lines

Gregor Mendel, the founder of modern genetics, was also interested in what pure lines were and worked on breeding them in plants. Mendel used 22 similar pea lines. Exploring variability in organisms, he formulated his famous laws. In addition, he noticed that pure lines under natural selection are often not viable.

In the wild, when external conditions change, a population with a certain set of genes often cannot change quickly.

Laboratory mice

It is difficult to overestimate how important laboratory mice are for science. They are used both in clinical studies and as experimental animals. Mice interested researchers because they reproduce very quickly. Laboratory mice were developed in the 19th century through inbreeding. After 18-20 generations they turn out absolutely identical.

They are used in research and medicine. Since they are absolutely identical, it is possible to compare the group receiving a particular drug and the control group. Moreover, the results are objective and repeatable, which is impossible to achieve using ordinary animals.

True, some scientists believe that calling laboratory mice a pure line is incorrect.

Individuals of the same group may differ in appearance from each other. This describes the concept of “reaction norm,” i.e., the possible range of differences in external signs.

So, what a pure line is is also well understood using the example of self-pollination of plants.

The use of pure lines of plants and animals in breeding together with modern methods of genetic engineering promises fantastic results. Maybe there will be no need to kill animals for meat? As in science fiction, animals will give meat from a living body? (And painlessly?) Or will we have plants that are not afraid of pests and with increased productivity?

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

Heredity– the ability of organisms to transmit their characteristics and developmental characteristics to their offspring.
Variability– a variety of characteristics among representatives of a given species, as well as the ability of descendants to acquire differences from their parent forms.
Genetics– the science of the laws of heredity and variability.

2. Describe the contribution of scientists you know 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 analysis of their offspring. This method was used by G. Mendel.
Genealogical - the study of genealogies. Allows you to determine 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 - study under a microscope of the chromosome set - the number of chromosomes, features of their structure. Allows detection of chromosomal diseases.

4. What is the essence of the hybridological method of studying the inheritance of characters?
The hybridological method is one of the methods of genetics, a way of studying the hereditary properties of an organism by crossing it with a related form and subsequent analysis of the characteristics of the offspring.

5. Why can peas be considered a successful object for genetic research?
Pea species differ from each other in a small number of clearly distinguishable characteristics. Peas are easy to grow; in the Czech Republic they reproduce several times a year. In addition, in nature, peas are self-pollinators, but in experiments, self-pollination is easily prevented, and the researcher can easily pollinate the plant with the same pollen from another plant.

6. Inheritance of which pairs of traits in peas was studied by G. Mendel?
Mendel used 22 pure pea lines. Plants of these lines had very pronounced differences from each other: the shape of the seeds (round - wrinkled); seed color (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 pure line?
A pure line in genetics is a group of organisms that have some characteristics that are completely transmitted to the 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 containing two identical allelic genes.
Heterozygous organism– an organism containing two different allelic genes.

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

3. Formulate a rule for the uniformity of first-generation hybrids.
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 the splitting rule.
When two descendants (hybrids) of the first generation are crossed with each other, in the second generation a split 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 gamete purity.
When formed, each of them includes only one of the two “elements of heredity” responsible for a given trait.

6. Using generally accepted symbols, draw up a diagram of monohybrid crossing.

Using this example, characterize the cytological basis of monohybrid crossing.
P is the parent generation, F1 is the first generation of descendants, F2 is the second generation of descendants, A is the gene responsible for the dominant trait, and A is the gene responsible for the recessive trait.
As a result of meiosis, the gametes of the parent individuals will contain one gene each, responsible for the inheritance of a certain trait (A or a). In the first generation, the 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 gene combinations will have the same phenotype (due to the presence of a dominant gene), while those with the fourth will have a different phenotype (recessive).

7. Solve the genetic problem of monohybrid crossing.
Task 1.
In watermelon, the green color of the fruit dominates over the striped color. By crossing a green-fruited variety with a striped-fruited one, first-generation hybrids with green-colored fruits were obtained. The hybrids were cross-pollinated and 172 second-generation hybrids were obtained. 1) How many types of gametes does a green-fruited plant produce? 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 color will there be in F2? 5) How many homozygous plants with green fruit color will there be in F2?
Solution
A – green color, and – striped color.
Since when crossing plants with green and striped fruits, plants with green fruit were obtained, we can conclude that the parent individuals were homozygous (AA and aa) (according to Mendel’s rule of uniformity of first-generation hybrids).
Let's draw up a crossing diagram.

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 long-haired cat crossed with a heterozygous short-haired cat produced 8 kittens. 1) How many types of gametes does a cat produce? 2) How many types of gametes does a cat produce? 3) How many phenotypically different kittens are there in the litter? 4) How many genotypically different kittens are there in the litter? 5) How many kittens in the litter have long hair?
Solution
A – short hair, and – long hair. Since the cat had long hair, she is homozygous, her genotype is aa. The cat has genotype Aa (heterozygous, short hair).
Let's draw up a crossing diagram.

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

Multiple alleles. Analysis cross

1. Give definitions of concepts.
Phenotype– a set of all signs and properties of an organism that are revealed in the process of individual development in 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?
The gene for any trait may have other “conditions” that cannot be called either dominant or 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 out the table.

Types of interaction of allelic genes

5. What is analytical crossing and what is its practical significance?
Test crossing is 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 crossing.
Task.

The white color of the phlox corolla dominates over the pink one. A plant with a white corolla was crossed with a plant with a pink color. 96 hybrid plants were obtained, of which 51 are white and 45 are pink. 1) What genotypes do the parent plants have? 2) How many types of gametes can a plant with a white corolla produce? 3) How many types of gametes can a plant with a pink corolla produce? 4) What phenotypic ratio can be expected in the F2 generation from crossing F1 hybrid plants with white flowers with each other?
Solution.
A – white color, and – pink color. The genotype of one plant A.. is white, the second aa is pink.
Since in the first generation there is a 1:1 split (51:45), the genotype of the first plant is Aa.
Let's draw up a crossing diagram.

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

Dihybrid cross

1. Give definitions of concepts.
Dihybrid cross– crossing of individuals in which differences from each other in two characteristics are taken into account.
Punnett grid is a table proposed by the English geneticist Reginald Punnett as a tool, which 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 shape of seeds.
Yellow smooth (AABB) × Green wrinkled (AABB) =
R: AaBv×AaBv (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 characteristics.
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 coloring in cats dominates over fawn, and short hair dominates over long hair. Purebred Persian cats (black longhaired) were crossed with Siamese cats (fawn shorthaired). 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, B – long hair.

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 one, and the red color of the fruit dominates over the yellow one. By crossing a heterozygous plant with a red color and pear-shaped fruits and a yellow-fruited one with round fruits, 120 plants were obtained. 1) How many types of gametes does a heterozygous plant with red fruit color and pear-shaped form form? 2) How many different phenotypes resulted from such a cross? 3) How many different genotypes resulted from this crossing? 4) How many plants were obtained with a red color and a rounded fruit shape? 5) How many plants were obtained with a yellow color and a rounded fruit shape?
Solution
A – round shape, and – pear shape.
B – red color, c – yellow color.
Let's 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 exchange of sections of homologous chromosomes during conjugation in prophase I of meiosis.
Chromosome map- this is a diagram of the relative position and relative distances between the genes of certain chromosomes located in the same linkage group.

2. In what case does the law of independent inheritance of characteristics 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 chromosomal 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 located linearly on chromosomes, that is, one after another.
During the formation of gametes, 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 end up in one 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 is the basis for compiling genetic maps of organisms?
Calculating the frequency of crossing over between any two genes on the same chromosome that are responsible for different traits makes it possible to accurately determine the distance between these genes, and therefore begin to build a genetic map, which is a diagram of the relative arrangement of genes that make up one chromosome.

7. Why are chromosome maps made?
Using genetic maps, you can find out the location of the genes of animals and plants and the information from them. This will help in the fight against various currently incurable diseases.

Hereditary and non-hereditary variability

1. Give definitions of concepts.

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

3. What determines the limits of modification variability?
The limits of modification variability depend on the reaction norm, 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 caused by 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 out the table.

Types of mutations

6. What is meant by mutagenic factors? Give relevant examples.
Mutagenic factors are influences that lead to the occurrence of mutations.
These can be physical influences: ionizing radiation and ultraviolet radiation, which damage 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.
Gene diseases– diseases caused by gene or chromosomal mutations.
Chromosomal diseases– diseases caused by changes in the number of chromosomes or their structure.

2. Fill out 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 in humans are inherited in a sex-linked manner?
Hemophilia and color blindness are inherited in humans in a gender-linked manner.

5. Solve genetic problems on 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 does a woman produce? 2) How many types of gametes are produced in men? 3) What is the probability of having a child with long eyelashes in this family (in%)? 4) How many different genotypes and how many phenotypes can there be among the children of a given couple?
Solution
A – long eyelashes
a – short eyelashes.
The female is heterozygous (Aa), since the father had short eyelashes.
The man 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, the free earlobe is dominant over the non-free earlobe, and the smooth chin is recessive to the chin with a triangular fossa. These traits are inherited independently. From the marriage of a man with a loose earlobe and a triangular dimple on the chin and a woman with a loose earlobe and a smooth chin, a son was born with a smooth chin and a loose earlobe. What is the probability of having a child in this family with a smooth chin and a loose earlobe; with a triangular dimple on the chin (%)?
Solution
A – free earlobe
a – non-free earlobe
B – triangular fossa
c – smooth chin.
Since the couple had a child with homozygous characteristics (aabv), the genotype of the mother is Aavv, and the genotype of the father is aaBv.
Let's write down the genotypes of the parents, types of gametes and the crossing scheme.

Let's create a Punnett lattice.

Answer:
1. 25
2. 50.

Task 3.

In humans, the gene causing hemophilia is recessive and is located on the X chromosome, while albinism is caused by an autosomal recessive gene. Parents normal according to these characteristics gave birth to an albino and hemophiliac son. 1) What is the probability that their next son will exhibit these two abnormal features? 2) What is the probability of having healthy daughters?
Solution:
X° - presence of hemophilia (recessive), X - absence of hemophilia.
A – normal skin color
a – albino.
Genotypes of parents:
Mother - X°HAa
Father - HUAa.
Let's create a Punnett lattice.

Answer: the probability of displaying signs of albinism and hemophilia (genotype X°Uaa) in the next son is 6.25%. The probability of having healthy daughters is (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 child (in%)?
Solution.
X° - presence of atrophy (recessive), X - absence of atrophy.
A – hypertension
a – no hypertension.
Genotypes of parents:
Mother - Х°Х°аa (since she is sick with atrophy and without hypertension)
Father - HUAa (since he is not sick with atrophy and his father had 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).

Explanation.

Answer.

In agrocenoses, cultivated plants, like weeds, are subject to the action of natural selection.

Explanation.

The instability of agrocenosis is also due to the fact that the protective mechanisms of producers - cultivated plants - are weaker than those of wild species, whose adaptations have been improved in the course of natural selection over millions of years. In agrocenoses the effect of natural selection is weakened. In agrocenoses, artificial selection operates, directed by man primarily to increase the productivity of agricultural crops. Natural ecosystems are capable of self-regulation. Agrocenosis is regulated by humans, and if it is not maintained, it will quickly collapse and disappear. Cultivated plants will not withstand competition with wild species and will be crowded out. In place of the agrocenosis, a natural biogeocenosis will form.

Individual selection– carried out according to the genotype, the result is the breeding of a pure line, i.e. a resistant variety.

Mutagenesis- this is the introduction of changes to the nucleotide sequence of DNA (mutations). There are natural (spontaneous) and artificial (induced) mutagenesis.

Population waves(waves of numbers, waves of life) - sharp fluctuations in the number of individuals in a population due to natural causes. Periodic or aperiodic fluctuations in the number of individuals in a population are characteristic of all living organisms without exception. The reasons for such fluctuations may be various abiotic and biotic environmental factors. The action of population waves, or waves of life, involves the indiscriminate, random destruction of individuals, due to which a genotype (allele) that was rare before a population fluctuation can become common and be picked up by natural selection. If in the future the population size is restored due to these individuals, this will lead to a random change in gene frequencies in the gene pool of this population. Population waves are a supplier of evolutionary material.

Classification of population waves

Periodic fluctuations in the number of short-lived organisms are characteristic of most insects, annual plants, most fungi and microorganisms. These changes are mainly caused by seasonal fluctuations in numbers.

Non-periodic fluctuations in numbers, depending on a complex combination of different factors. First of all, they depend on relationships in food chains that are favorable for a given species (population): a decrease in predators, an increase in food resources. Typically, such fluctuations affect several species of both animals and plants in biogeocenoses, which can lead to radical rearrangements of the entire biogeocenosis.

Outbreaks in the number of species in new areas where their natural enemies are absent.

Sharp non-periodic fluctuations in numbers associated with natural disasters (as a result of drought or fires).