Question

analyze the table below and answer the question that follows.
if the ability to roll ones tongue is dominant (r) and the inability to roll ones tongue is recessive (r), what would the genotype be for someone who can not roll their tongue?
a. rr and rr
b. rr
c. rr and rr
d. rr

Explanation:

Step1: Understand dominant and recessive traits

In genetics, a dominant trait (R) shows its effect even if an individual has only one copy of the allele. A recessive trait (r) shows its effect only when an individual has two copies of the recessive allele.

Step2: Analyze each option

• Option A: RR is homozygous dominant (can roll tongue), rr is homozygous recessive (cannot roll tongue). But the question asks for someone who cannot roll tongue, so having RR is incorrect.
• Option B: Rr is heterozygous. Since R (dominant) is present, a person with Rr can roll the tongue.
• Option C: Rr (can roll tongue) and rr (cannot roll tongue). But we need only the genotype for non - rollers.
• Option D: rr is homozygous recessive. With two recessive alleles, the person cannot roll the tongue.

Answer:

D. rr