Question

True/ False

Directional selection acting upon a beneficial recessive allele will take longer to push this allele to fixation than for a beneficial dominant allele. Assume the selection coefficient is the same for each case.

True/ False

When the strength of selection is weak (s is very small) and the population size is also very small (so N_e is also very small), natural selection will dominate allele frequency change through time.

Answer 1

1)True

Explanation:

  A dominant allele produces a dominant phenotype in individuals who have one copy of the allele, which can come from just one parent. For a recessive allele to produce a recessive phenotype, the individual must have two copies, one from each parent. An individual with one dominant and one recessive allele for a gene will have the dominant phenotype. They are generally considered “carriers” of the recessive allele: the recessive allele is there, but the recessive phenotype is not.

2)True

Explanation:

Genetic drift, unlike natural selection, does not take into account an allele’s benefit (or harm) to the individual that carries it. That is, a beneficial allele may be lost, or a slightly harmful allele may become fixed, purely by chance.

A beneficial or harmful allele would be subject to selection as well as drift, but strong drift (for example, in a very small population) might still cause fixation of a harmful allele or loss of a beneficial one.