[Campbell Biology P.1171] Red-green color blindness is X-linked in both humans and squirrel m... | Practice Question

Red-green color blindness is X-linked in both humans and squirrel monkeys. However, the text implies that the inheritance pattern might not be "apparent" in squirrel monkeys in the same way it is in humans. Based on the provided text, which of the following best explains this difference?

  • A: Human males are affected by a single mutant X chromosome, while all male squirrel monkeys are red-green color-blind due to only having one red/green sensitive opsin gene allele on their X chromosome, making the inheritance pattern less about a 'mutation' appearing.
  • B: Squirrel monkeys have a different number of sex chromosomes than humans, which alters X-linkage.
  • C: The red/green opsin gene is X-linked in humans but not in squirrel monkeys.
  • D: Squirrel monkeys have an autosomal gene that compensates for red-green color blindness.

Explanation

The text explains that human males are affected by a single mutant X chromosome for red-green color blindness. In contrast, it states that all male squirrel monkeys are red-green color-blind because they only have two opsin genes: one for blue light and another X-linked gene that is sensitive to either red or green, depending on the allele. This means that red-green color blindness is the default state for male squirrel monkeys, rather than a deviation caused by a mutation, making the inheritance pattern less 'apparent' as a variable trait within the male population.