Genetic drift is the random fluctuation of allele frequencies in a population due to chance events. It is one of the most significant mechanisms of evolution. The frequency of an allele in an isolated population may change due to genetic drift.

Factors that contribute to genetic drift are:

1. Small population size: In a small population, chance events can have a significant impact on the frequency of alleles. This is because the genetic makeup of a small population is more vulnerable to random fluctuation.

2. Non-random mating: Non-random mating can also contribute to genetic drift. Inbreeding, for example, can lead to an increase in the frequency of harmful recessive alleles.

3. Natural disasters: Natural disasters such as earthquakes, floods, and wildfires can cause a significant reduction in population size. This can lead to a loss of genetic diversity and an increase in the frequency of certain alleles.

4. Founder effect: The founder effect occurs when a small group of individuals establishes a new population. The genetic makeup of this new population is determined by the alleles present in the founding individuals. This can lead to a significant deviation from the genetic makeup of the original population.

5. Genetic bottleneck: A genetic bottleneck occurs when a population undergoes a significant reduction in size. This can lead to a loss of genetic diversity and an increase in the frequency of certain alleles.

In conclusion, genetic drift can cause a change in the frequency of an allele in an isolated population. This occurs due to chance events such as small population size, non-random mating, natural disasters, founder effect, and genetic bottleneck.

It may be due to mutation also. Bcoz genetic drift takes place in small populations. And mutation is a random change and it can take place anywhere