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

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.

luisvaschetto luisvaschetto · Answer 2 · 2021-11-23T16:41:11+01:00

The member of the couple's family who is this most likely to be colorblind is the child's maternal grandfather.

An X-linked recessive inherited genetic trait is transmitted from parent to child through mutations in genes localized on the X chromosome.

In males, X-linked recessive traits are always expressed because males contain only one X chromosome.

In consequence, in this case, the mother should be a normal carrier of the disease/condition, thereby her dominant X-linked allele can mask the expression of the recessive (daltonic) allele, which is passed to the child from the maternal grandfather.

In conclusion, the member of the couple's family who is this most likely to be colorblind is the child's maternal grandfather.

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