Question

Colorblindness is a sex-linked trait. A mother with normal vision and a man who is colorblind have a colorblind daughter. What statement MUST be true about the parents?

Answer 1

Answer:

The child must have a father who is colorblind and a mother who is a carrier/ is colorblind.

Explanation:

The genetic code for color blindness is carried upon the x chromosome. This means that a male- who has only one X chromosome- only needs their mother to be a carrier to be colorblind. Women on the other hand, need two to be color blind, as the faulty x chromosome can be weeded out by the other.

Therefore, the father, in order to pass on the colorblindness, must be colorblind himself, whereas the mother only needs to be a carrier (or can be completely color blind herself).

Answer 2

Answer:

A) The mother is a heterozygous carrier

Explanation:

A) The mother is a heterozygous carrier.   - only one that makes sense

B) The father is a heterozygous carrier.  - he is double recessive

C) The mother cannot have the colorblind gene. - that is possible

D) The mother is homozygous dominant for normal vision. - that would mean the 100% of the offspring would be normal