Question

Red, green colour blindness is a sex-linked trait. Which of the given statements is not correct regarding colour blindness?

• A. Homozygous recessive condition is required for the expression of colourblindness in females
• B. Males can be carriers of the trait
• C. Colourblind women always have colourblind father and always produce colourblind son
• D. It is more common in males than in females

Answer 1

The correct option is B Males can be carriers of the trait

Colour blindness is a common hereditary (inherited) condition The gene (allele) b for colour blindness is recessive to the gene B for normal vision. The gene b is carried only on the X chromosome. X-linked red-green color blindness is a recessive trait. Females heterozygous for this trait have normal vision, while males heterozygous for this trait, which have only one X chromosome will always be affected(diseased).

Red/green colour blindness is passed from mother to son on the 23rd chromosome, which is known as the sex chromosome because it also determines sex. Since colorblindness is a sex-linked recessive trait and males just have one X chromosome, they can never be the carriers. Males will always express the disease/phenotype.
So, the correct answer is (C).