U4 AOS2 Topic 3: Genetic Drift and Gene Flow

Genetic drift:

Genetic drift is a random event that changes a population’s allele frequency and effects genetic diversity of a population. Genetic drift can be described in two ways i.e. bottleneck effect and founder effect.

Bottleneck effect: This can occur through a random event such as natural disaster that wipes out a portion of a population. This decreases the size of population and affects the allele frequency as some of the alleles are lost in this event. The new population being smaller in size has decreased genetic diversity.

Founder effect: When a portion of population that does not represent the characteristics of that population separates from the population to make a new colony or population in a new region. The new population formed has a lower genetic diversity compared to the original population.

                    

Gene flow:

It is the flow or transfer of alleles into and out of the population. Gene flow can result from two ways which are as follows:

1.   Interbreeding: two individuals from different populations can interbreed and cause gene flow. An individual from one population interbreeds with an individual from another population and transfers its alleles into that population.

2.   Migration: individuals from one population can migrate to another population either by immigration or emigration. Immigration of individuals into a population can add its alleles to that population increasing its genetic diversity whereas; emigration of individuals from a population can remove the alleles from that population decreasing its genetic diversity.