Question

in humans, the allele for rh factor comes in two forms: rh⁺ and rh⁻. inheritance of the alleles determines whether an individual has either rh⁺ blood or rh⁻ blood.
to identify the dominant form of the allele, which of these questions is the most useful to investigate?
a. which of the two alleles is more common in the human population?
b. which of the two blood types is more common in the human population?
c. which blood type forms when an individual receives two copies of one of the alleles?
d. which blood type forms when an individual receives one copy of each allele?

Explanation:

To determine the dominant allele (Rh⁺ or Rh⁻), we analyze each option:

• Option A: Asking which allele is more common does not directly indicate dominance (frequency ≠ dominance).
• Option B: Asking which blood type (Rh⁺ or Rh⁻) is more common also does not indicate dominance (frequency of phenotype ≠ dominance of allele).
• Option C: If an individual has two copies of an allele (homozygous), the blood type formed shows the allele's expression. But for dominance, we need to see the phenotype in heterozygotes. However, this is closer than A/B. Wait, no—wait, the key is: Dominance is determined by the phenotype of a heterozygote (having one copy of each allele). Wait, no, let's re - evaluate. Wait, the question is to identify the dominant form of the allele. Dominance is about which allele is expressed in the heterozygous condition.
• Option D: If an individual receives one copy of each allele (heterozygous), the blood type formed will show which allele is dominant (since the dominant allele's phenotype is expressed in heterozygotes). For example, if heterozygous (Rh⁺/Rh⁻) has Rh⁺ blood, then Rh⁺ is dominant. So Option D is the most useful because it directly tests the heterozygous condition, which is the basis for determining dominance.

Answer:

D. Which blood type forms when an individual receives one copy of each allele?