Factors affecting alleles frequency

1.      Genetic Drift

a.       Founder effect

It occurs when small groups of individuals colonises a geograpically isolated area or new area such as island. The range and frequency of allel in this small group are unlikely to be representative of those original population. Alleles maybe more or less frequent.

b.      Bottleneck effect

Population may suddenly reduce in number. It usually from a catastropic environmental changes like fire, flood, or by sudden severe sellection pressure. This happen often by human activities such as rapid habitat destruction.

2.      Natural Selection

Population produce more offspring than environmental resources can maintain.  So there must be a competition among them to get spaces and food. Individual with the best adaptation can survive and reproduce to pass their successful alleles to the offspring. The frequency of succesfull alleles will increase in the gene pool. Environmental factors act as selecting agents of phenotype. When the environment change, different phenotpe will be selected for. After a certain number of generations, frequencies allel and phenotype might change so markedly that population becomes reproductively isolation from others of that species.

3.      Mutation

Mutation is souce of new allel in gene pool. If mutation occurs in the gamet producing cell during DNA replication for meiosis and gamet is fertilize, then the mutation will enter the gene pool. Alleles resulting from unfavourable mutation are selected against and only remain in the gene pool if they are recessive.

4.       Nonrandom mating

Individual of many species only have a choice about which parter to mate with. But in the random mating, individual have choices about the parter. The result is that individual have more opportunity to mate than other and produce more offspring.

5.       Migration

Migration is movement of individuals from population to another. There are 2 types of migration. The first is imigration. Imigration is movement of individuals into a new population. Imigration may add new allel to a population, increasing population’s genetic diversity. The final population after imigrant arrive will increase in allel frequency.

The second is emigration. Emigration occurs when individual migrates out of the population. Emigration will remove alleles in population. Therefore, it will reduce the population’s genetic diversity. Population after immigrant have left have reducing of alleles frequencies. Both of this processes allow for gene flow between population and change the frequency of allel in population.

I will update this topic later when i have more time to read new book or other resources. i write this based on what i have learned from lecturer. i have an exam for next week. wish me luck :3