Question

How does purifying selection differ from positive selection?

1) Purifying selection removes deleterious alleles.
2) Positive selection results in more non-synonymous substitutions than purifying selection.
3) Purifying selection is a common form of disruptive selection.
4) All of the above are true.

Answer 1

Purifying selection removes deleterious alleles, while positive selection results in more non-synonymous substitutions.

Step-by-step explanation:

Purifying selection differs from positive selection in several ways:

1. Purifying selection removes deleterious alleles: This type of selection acts to eliminate harmful or deleterious alleles from a population, resulting in an overall decrease in genetic variation.
2. Positive selection results in more non-synonymous substitutions than purifying selection: Positive selection favors the spread of advantageous alleles in a population, which leads to an increase in non-synonymous substitutions (i.e., changes in the genetic code that result in a different amino acid being coded).

Therefore, the correct answer is: Option 1, Purifying selection removes deleterious alleles; Option 2, Positive selection results in more non-synonymous substitutions than purifying selection.