Cutting- edge science

August | 2020
CUTTING- EDGE SCIENCE
GENETICS AND ITS TYPES
Tuychiyeva Shoxista Shamsiyevna
biology teacher of 32 schools of Kushrabot district, Samarkand region
Abstract. The concept of population and pure line was proposed in 1907 by Johannsen.
A population is a group of animals and plants that belong to the same species, spread over
a certain area, and reproduce in isolation from other populations.
Key words: Animals of a particular breed or herd, heterozygosity and polymorphism,
mutational pressure and its directions.
The pure line differs from the population in that it consists of plants with a homozygous
degree, that is, plants with a similar genotype.But in a pure line, homozygosity is never
complete, because the genetic similarity of the line changes as a result of natural
mutations.There are no pure lines in animals. Although homozygosity has increased as
a result of inbreeding, there has been a sharp decline in productivity and vitality in
children.Therefore, without the creation of such lines in animal husbandry, they often
work with populations in the breeding of breeds and herds.Iogannsen was the first to
discover that the diversity of genotypes in a population and the same selection of
organisms on a pure line lead to different results. No progress was made when Iogannsen
conducted a selection of bean grain sizes on different lines for 6 years.It was observed
that the derived generations always returned to the mean of the line, i.e., a regression
event. Thus, in the absence of genotypic variability, selection was found to be ineffective.The
reason for the sharp difference in the outcome of the selection in the population and
in the pure lines is that they are genetically different in structure.The variability in the
population is so large that it consists of two parts, genetic and non-genetic
variability.Variability in the pure line is a phenotypic variability that occurs mainly
under the influence of external environmental factors.It has been found that this variability
is not passed on to offspring.Selection works primarily with genotypic variability.The
major private genetic sciences mentioned above are further subdivided into smaller
private genetic sciences that study the genetics of individual organisms, series. For
example, the following special genetic sciences have emerged in the field of plant
genetics: wheat genetics, potato genetics, cotton genetics, and others.Genetic sciences
are classified according to the methods used in scientific research as follows: Ontogenetics
(phenogenetics) - the study of the laws of development of traits and characteristics of
an organism in the process of ontogeny (personal development) in its phenotype as a
result of gene activity. Cytogenetics is a science that uses the method of hybrid genetic
analysis in a complex way with the cytological method.Mutational genetics is the study
of the laws of mutational (genetic) change in the genotype of organisms. Ecological
genetics is the study of the influence of environmental factors on the development of the
genotype of an organism as a phenotype. It creates ways to solve the problem of protecting
their gene pool from the negative effects of the extreme factor.Population genetics is the
study of the qualitative and quantitative composition of a population's gene pool, the
distribution of genes and genotypes in a population, and the laws of distribution. Medical
genetics - develops the genetic basis of methods for diagnosing and treating the causes
of hereditary diseases in humans.Molecular genetics is the study of the structure and
function of genes, which are the material basis of heredity and variability. Genetic
engineering - conducts practical research on genes and chromosome engineering based
on the theoretical advances of molecular genetics.Transgenic plants are involved in
creating new forms by creating animal forms, transplanting certain chromosomes or a

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