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A girl's father was color-blind (caused by a recessive X-linked allele), but neither her mother nor her mother's family had any occurrences of color-blind individuals. The girl marries a color-blind male. What can they assume for their children?

a) All sons will be color-blind, and all daughters will be carriers
b) All sons will be unaffected, and all daughters will be carriers
c) All children will be color-blind
d) Sons will be color-blind, and daughters will be unaffected

User Siraj
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1 Answer

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Final answer:

Each son has a 50% chance to be color-blind, and each daughter has a 50% chance to be color-blind or a carrier, since both parents provide an X chromosome with potential color-blindness alleles.

Step-by-step explanation:

Color blindness is a X-linked recessive trait, which means that a female can only express the trait if she inherits the recessive allele from both parents, while a male will express the trait if he inherits the recessive allele from his mother as males have only one X chromosome. In the case of the girl whose father is color-blind, she will be a carrier because she must have inherited one recessive allele (for color blindness) from her father and one normal allele from her mother. Since the girl's husband is color-blind, we can infer that he carries the recessive allele on his only X chromosome. When this couple has children, their sons will inherit the Y chromosome from their father and either the normal X or the X with the color-blindness allele from their mother. This means that there is a 50% chance for each son to be color-blind. Daughters, on the other hand, will inherit their father's color-blind X-chromosome and will either inherit a normal or color-blind X from their mother, resulting in a 50% chance of being color-blind.

Therefore, the statement that 'all children will be color-blind' is incorrect because daughters might inherit the normal allele from their mother, and not all sons will necessarily inherit the color-blind allele; it's a 50-50 chance for both genders. Hence, the final answer in two line explanation in 300 words could be: Each child has a 50% chance of being color-blind, with sons inheriting the condition if they receive the color-blind X from their mother, and daughters if they inherit the color-blind X from both parents.

User JFer
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