Question

For each selection coefficient, indicate whether the probability of fixation for a new mutation is higher in a large or small population or whether it is approximately equal in both population sizes. Please explain your reasoning. No actual calculations are required. However, to be concrete, assume that N for the small population is 100 and N for the large population is 10,000. (a) Strongly deleterious mutation: s=-0.1 (b) Weakly deleterious mutation: s=-0.001 (c) Neutral mutation: s=0 (d) Weakly beneficial mutation: s=0.001

Answer 1

When allele frequencies within a population change randomly with no advantage to the population over existing allele frequencies, the phenomenon is called genetic drift.

Smaller a population, the more susceptible it is to mechanisms such as genetic drift as alleles are more likely to become fixed at 0 (absent) or 1 (universally present).

Random events that alter allele frequencies will have a much larger effect when the gene pool is small.

Genetic drift and natural selection usually occur simultaneously in populations, but the cause of the frequency change is often impossible to determine.

Natural selection have effect on allele frequency. If an allele relates to a phenotype that enables an individual to better survive or have more offspring, the frequency of that allele will increase. Because offspring will also carry the beneficial allele and, therefore, the phenotype, they will have more offspring of their own that also carry the allele. Gradually , the allele will spread throughout the population and may become fixed: every individual in the population carries the allele. If an allele is dominant but detrimental, it may get eliminate from the gene pool when the individual with the allele does not reproduce. However, a detrimental recessive allele can remain for generations in a population, hidden by the dominant allele in heterozygotes. In such cases, the only individuals to be eliminated from the population are those unlucky enough to inherit two copies of such an allele.

Deterious mutation is defined as genetic alteration that increases an individual's susceptibility or predisposition to a certain disease or disorder. When such a variant along with the mutation  is inherited, development of symptoms is more likely, but not certain.