The four major factors that are responsible for changing gene frequency are as follows:
1. Gene mutations :induce hereditary alterations either in a solitary gene or across an entire chromosome.
2. Natural selection:instigates modifications in the gene frequency within a population, subsequently fostering evolutionary changes over time.
3. Migration :engenders the relocation of populations, facilitating the transfer of genetic material from one population to another.
4. Genetic drift :manifests as haphazard or unforeseen alterations in gene frequencies, arising purely by chance and accumulating gradually across generations.