Why is sex-linked red-green color blindness substantially more prevalent among human males than among females?
Answer and explanation
Correct answer: D. males possess only one X chromosome and express the recessive allele if inherited
- Step 1: Red-green color blindness is an X-linked recessive trait. Step 2. Males are hemizygous (XY); a single recessive allele on their sole X chromosome results in the condition. Step 3. Females (XX) require two recessive alleles to be affected; a single recessive allele makes them asymptomatic carriers. Answer: males possess only one X chromosome and express the recessive allele if inherited. Why not the others: Females have XX, not XY; the gene is on the X chromosome, not Y; testosterone does not denature opsins.
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