All are true regarding the genetic drift except -

Options

A. It mostly occurs in smaller populations
B. Certain alleles can be lost for ever because of genetic drift.
C. Founder effects and bottleneck effects are causes of genetic drift.
D. Mutations are primarily responsible for genetic drift.

Answer

To solve the question regarding which statement about genetic drift is false, we will analyze each option provided:

1. **Genetic drift mostly occurs in smaller populations.**
- This statement is true. Genetic drift has a more pronounced effect in smaller populations because random events can lead to significant changes in allele frequencies.

2. **Certain alleles can be lost forever because of genetic drift.**
- This statement is also true. Genetic drift can lead to the loss of certain alleles from a population, especially in small populations, where chance events can eliminate alleles entirely.

3. **Founder's effect and bottleneck effect are causes of genetic drift.**
- This statement is true as well. Both the founder's effect (when a new population is established by a small number of individuals) and the bottleneck effect (when a population's size is significantly reduced) are mechanisms that can lead to genetic drift.

4. **Mutations are primarily responsible for genetic drift.**
- This statement is false. While mutations introduce new alleles into a population, genetic drift is primarily a random process that affects allele frequencies due to chance events, rather than being driven by mutations.

Based on the analysis, the correct answer to the question is that the fourth statement is the one that is not true regarding genetic drift.

**Final Answer: The statement that is not true regarding genetic drift is: "Mutations are primarily responsible for genetic drift."**

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