Question

Red-green color blindness is a human X-linked recessive disorder. The normal allele, XB, is dominant to the mutant allele, Xb. ill has normal color vision, but her father is color blind. Jill marries Tom, who also has normal color vision. Jill and Tom have a daughter who has Turner syndrome and is color blind How and from whom did the daughter inherit color blindness? O O O O O an ovum carrying X3 followed by fertilization by sperm from a paternal nondisjunction event a maternal nondisjunction event followed by fertilization by sperm carrying Xb an ovum carrying X followed by fertilization by sperm from a paternal nondisjunction event a maternal nondisjunction followed by fertilization by sperm carrying XB a maternal nondisjunction followed by fertilization by sperm lacking sex chromosomes

Answer 1

1.

The third option is correct.

The daughter could not have inherited this allele from her father since, her father was normal.

Since, in case of colour blindness, males need to be affected in order to carry the disease.

She could only inherit this one allele from her mother, and it got expressed as she did not have another X chromosome which could be normal, due to Turner syndrome, that is, paternal non-disjunction event.

Hence, the ovum with chromosome X^b fused with the sperm from the father containing no chromosomes, giving rise to genotype X^b O.

Since no specific question has been asked, only the first question has been answered.

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