Question

Color blindness is a recessive trait that is carried on the human X chromosome.
Which of the following would not be true of this gene's pattern of inheritance?

• A. Color blind females would carry the trait on both of their sex chromosomes.
• B. Color blind males would carry the trait on only one of their sex chromosomes.
• C. Females that had the trait on only one of their X chromosomes would not be color blind.
• D. Males and females with color blindness would be present in approximately equal numbers.

Answer 1

Answer: (D)

Males and females with color blindness would be present in approximately equal numbers.

Color blindness is a recessive trait present on the X chromosome. Since, human females have two X chromosomes, both the chromosomes should carry the recessive gene for the trait to be expressed, however as human males have one X and the other Y chromosome. The recessive trait gets expressed whenever present. Therefore, the ratio of expression will be different in both males and females. The number of affected males will be greater than the number of females.

So, the correct answer is 'Males and females with color blindness would be present in approximately equal numbers'