The illustration above represents a cross between a colour blind male and normal female. Study it carefully and answer the questions. Which of the genotypes...

The illustration above represents a cross between a colour blind male and normal female.
Study it carefully and answer the questions.

Which of the genotypes are carriers of colour blindness?

Answer Details

Genotypes 1 and 11 are carriers of color blindness. This is because color blindness is a recessive trait that is carried on the X chromosome. In this cross, the male is color blind because he only has one X chromosome, and it carries the recessive gene for color blindness. The female is not color blind because she has two X chromosomes, and she would need to have two copies of the recessive gene to be color blind. Genotype 1 represents the X chromosome that the color blind male passes on to his daughters, and genotype 11 represents the X chromosome that the normal female passes on to her sons. Since both of these genotypes carry one copy of the recessive gene for color blindness, they are carriers of the trait. Genotype 111 represents the X chromosome that the normal female passes on to her daughters. Since this X chromosome does not carry the recessive gene for color blindness, genotype 111 is not a carrier of the trait. Therefore, the correct answer is 1 and 11 only.