What is genetic drift??? 5

This doesn't want to be a computer problem.

On the one hand, the role of mutation in the evolution of species is manifested in the fact that mutation itself is a force that affects gene frequency; On the other hand, mutation provides the raw material for natural selection and is the main material for evolution. Mutations can be divided into non-frequent mutations and frequent mutations, the former refers to a single mutation that occurs infrequently in the whole population and has little effect on gene frequency; The latter refers to the frequent occurrence of a certain mutation in a large population, which has a greater impact on gene frequency.

Genetic drift refers to the phenomenon of random increase, decrease or even loss of gene frequency due to a population being too small. Drift can occur in all populations, and the change in gene frequency in large populations is small and negligible. When the population is small, the effect of drift is obvious.

This fluctuating change leads to the disappearance of some alleles and the fixation of others, thus altering the genetic structure of the population. In large populations, fluctuations in the number of children born to individuals with different genotypes have no significant effect on gene frequency. The small number of people in the small group is small and isolated from the total population, and this social and geographical factor forms a small group, the A gene is fixed (A = 1), and the A gene has few people, and if the A gene has no children, the A gene will disappear in the population relatively quickly, causing random fluctuations in gene frequency in this small group.

This drift is related to the size of the population, the smaller the population, the faster the drift speed, and even 1 or 2 generations will cause the fixation of one gene and the disappearance of another gene to change its genetic structure, while the drift of large groups is slow and can reach genetic equilibrium randomly.

For example, if the frequency of a gene in a population is 1%, if there are 1 million individuals in the population, there will be thousands of individuals containing this gene. If there are only 50 individuals in this population, then only 1 individual has this gene.

In this case, this gene may disappear from the population due to the accidental death of the individual or the failure to mate. This phenomenon is known as genetic drift.

The frequencies of some heterolytic commas genes are particularly high in small isolated populations, which may be due to the fact that the genes possessed by a small number of ancestors in this group gradually reach a higher level due to genetic drift, a phenomenon called the founder effect. For example, 5% of people on East Carolina Island in the Pacific Ocean suffer from congenital blindness. According to the survey, at the end of the 18th century, due to the typhoon, there were only 30 people left on the island, and they bred into a small group of more than 1,600 people in Yanxun today, and the 5% blindness may only be a carrier of one of the original 30 founders, whose gene frequency q=1 60=, after several generations of isolation and breeding, q soon rose to, which is the founder effect.