LESSON 3: Genetic Diversity
Gene Flow and Genetic Drift
While multiple versions of a gene (like the coat colour gene) are called alleles. Genetic drift is an occurrence that causes the allele frequencies to change in a population. Random removal of individuals from the population can make the proportions of an allele shift from its starting.
There are two main examples of this: the bottleneck effect and the founder effect.
The founder effect occurs when a small non-representative portion of the gene pool is displaced, forming a new, less genetically diverse population. Similarly, when a large portion of a population is removed by unfavourable conditions like famine, disease, or climate change, the genetic diversity can be limited as some alleles are lost all together. This is called the bottleneck effect. Smaller population are more susceptible to genetic drift as there are less copies of each allele, making losses due purely to chance more likely.
Gene flow is the transfer of alleles through migration or emigration of individuals between populations. While it can help mitigate diversity lost by genetic drift, it can also retard the effects of speciation.