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Difficulty: HardGenetics and Heredity

In human sex-linked inheritance, a biological male displaying an X-linked recessive trait must have inherited the causal allele from his mother, and will inevitably pass that allele to all of his biological daughters.

Answer: Answer

Answer

True
Because biological males have an XYXY genotype, they receive their single X chromosome carrying the recessive allele from their mother. When an affected male reproduces, he passes his Y chromosome to all sons and his single X chromosome carrying the mutant allele to all daughters.

Step-by-Step Solution

1
Analyze the chromosomal sex determination in males and females
Biological males possess XYXY sex chromosomes, while biological females possess XXXX sex chromosomes.
Understanding sex chromosome distribution is essential for tracking sex-linked allele transmission.
2
Determine maternal inheritance for affected males
An affected male (XrYX^r Y) receives his Y chromosome from his father and his XrX^r chromosome exclusively from his mother.
The Y chromosome does not carry X-linked genes, meaning the recessive allele must come from the maternal gamete.
3
Determine paternal transmission to female offspring
All biological daughters receive the father's single X chromosome (XrX^r) and one maternal X chromosome.
Fathers invariably contribute their X chromosome to female offspring, making all daughters inherit the paternal allele.

Key Concept

Sex-Linked Inheritance and Hemizygosity
Estimated Time:1m 0s
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Topics

Genetics and Heredity

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