Color blindness is a recessive X-linked trait. A normal couple has a color-blind child. At least one member of the couple's families is colorblind, who is this most likely to be?a) the child's paternal grandmotherb) the child's paternal grandmother or grandfatherc) the child's maternal grandmotherd) the child's paternal grandfathere) the child's maternal grandfather

c or e

Explanation:

The correct answer would be the child's maternal grandmother or grandfather.

For X-linked traits, only females can be carriers while males are either affected or totally free from the trait. This is because females have two X (XX) chromosomes while males have only one (XY).

Since the couple is normal, it means the father is free from color blindness. The only available option now is the mother and since she is phenotypically normal, it means that she is a carrier of the disease. She must have inherited the allele from either of her parents, but not from both. If she had inherited an affected X chromosome from each of her parents, she would have been phenotypically affected for color blindness.

Hence, the child's color-blind allele can only be traced back to either of the child's maternal grandmother or grandfather.

The correct option is c or e.