Question

Consider an allele, present at very low frequency in a population, that causes individuals carrying it to have a higher fitness than the common (i.e. wild-type) allele at that locus Gi.e. there is directional selection favouring this allele). Will this beneficial allele rise in frequency faster if it is dominant or if it is recessive? Explain your answer in three sentences or less.

Answer 1

Answer:

The beneficial allele will rise faster if it is dominant

Explanation:

A dominant allele is expressed even if there is only one (heterozygous) allele present in an individual, whereas a recessive allele requires 2 copies (homozygous). If the allele confers fitness, it is much more likely to be acted on by natural selection if the allele is dominant, as the carrier will actually possess the associated phenotype.

For a recessive allele to be confer fitness, an individual would need to be homozygous. Even if two individuals both heterozygous for this rare allele had children, those children would have only a 1:4 chance of being homozygous, meaning its beneficial effects would rarely be seen and it would take much longer to rise in frequency.