Multiple Choice
X-linked recessive traits in humans (or in Drosophila) are observed most frequently in which group?
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2. Mendel's Laws of Inheritance
Sex-Linked Genes
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A woman is red-green color-blind. What can we conclude, if anything, about her father?
A
He could be either color-blind or have normal vision.
B
He must be red-green color-blind.
C
No conclusion can be drawn about his color vision.
D
He must have normal color vision.
Verified step by step guidance1
Recall that red-green color blindness is a sex-linked recessive trait located on the X chromosome.
Since the woman is red-green color-blind, she must have two copies of the mutant allele (one on each X chromosome), making her genotype X^cX^c, where X^c represents the X chromosome carrying the color-blind allele.
A female inherits one X chromosome from her mother and one X chromosome from her father. Therefore, the woman’s father must have contributed an X^c chromosome.
Because males have only one X chromosome (XY), if the father contributed an X^c chromosome, he must be color-blind himself (genotype X^cY).
Thus, we can conclude that the woman’s father must be red-green color-blind.
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