Population Genetics. Analysis gene pool of population.

Date: 2015-10-07; view: 433.

THE BASIC THEORETICAL ITEMS OF INFORMATION

Population genetics of is the part of genetics studying regularities of gene pool existence and laws of variability within populations.

A population is a group of individuals of one species living in the same geographical area and sharing a common gene pool. Or a population is a group of potentially interbreeding organisms of the same species occupying a certain area.

The gene pool is the sum of all genetic information carried by the members of a population.

Members of a population vary from one another. This variation is the raw material on which natural selection operates. The main tasks of the population genetic are analysis of and gene pool's changes. The specific tasks are:

· Analysis of the genetic structure of population

· Determination of the frequencies of alleles of a particular gene in a given population

· Predication of allele frequencies in future generations.

Genetic structure of population is ratio of dominant and recessive homozygotes and heterozygotes.

The Hardy-Weinberg Law can be used to determine the frequencies of alleles of a particular gene in a given and predict allele frequencies in future generations. The law read as follows:

Under the appropriate conditions (in case of ideal population) there will be no change in gene frequencies.

The law requires the following assumptions that are the characteristics of an ideal population:

the population mates randomly

no mutations occur

no selection occurs (no influence of “fitness”)

no migration (no gene flow)

no isolations (within population)

no population waves

large population size (no genetic drift)

For a given gene A with alleles frequencies p (dominant) and q (recessive) in a parental population the next generation will be in equilibrium (the gene frequencies p and q will not change over time).

p = the frequency of the dominant allele

q = the frequency of the recessive allele

and

p² = the frequency of the homozygous dominant individuals

2pq = the frequency of the heterozygous individuals

q² = the frequency of the homozygous recessive individuals

Hardy-Weinberg equilibrium is represented by the following equations:

p² + 2pq + q² = 1

p + q = 1

It is important to note the following:

The frequencies of alleles are represented by p and q.

The frequencies of individuals are represented by p², 2pq, and q²

Remember that both the homozygous dominant and heterozygous individuals will express the dominant trait (p² + 2pq).

These conditions of the Hardy-Weinberg law are rarely met, so allele frequencies in the gene pool of a population do change from one generation to the next, resulting in evolution. We can now consider that any change of allele frequencies in a gene pool indicates that evolution has occurred. The Hardy-Weinberg law proposes those factors that violate the conditions listed cause evolution. A Hardy-Weinberg equilibrium provides a baseline by which to judge whether evolution has occurred. Hardy-Weinberg equilibrium is a constancy of gene pool frequencies that remains across generations, and might best be found among stable populations with no natural selection or where selection is stabilizing. Microevolution is the accumulation of small changes in a gene pool over a relatively short period.