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Zorluk: Çok zorGenetics and Heredity

In human inheritance, a father who is affected by an X-linked dominant condition will pass the disorder to 100% of his daughters and 0% of his sons, whereas a mother who is heterozygous for the same condition will pass it to approximately 50% of her offspring regardless of their biological sex.

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The statement is true.
The statement is completely accurate. Biological males (XYXY) pass their XX chromosome to all biological daughters and their YY chromosome to all biological sons. If a male has an X-linked dominant disorder, all his daughters will receive that dominant allele (XDX^D) and express the trait. Since sons only receive his YY chromosome, none will inherit the X-linked condition from him. Conversely, biological females (XXXX) pass one of their two XX chromosomes randomly to each child. A heterozygous female (XDXdX^D X^d) has a 1 in 2 (50%) chance of passing on the affected allele to any offspring, regardless of sex.

Adım Adım Çözüm

1
Determine the sex chromosomes inherited from the father.
The father passes his XX chromosome to all daughters and his YY chromosome to all sons.
This establishes which offspring can potentially inherit an X-linked trait from the father.
2
Analyze the expression of the dominant trait in the daughters.
100% of the daughters inherit the father's affected XX chromosome and will express the condition.
A dominant trait only requires one copy of the allele to be expressed in the phenotype.
3
Analyze the transmission to the sons.
0% of the sons inherit the trait from the father.
Sons inherit the YY chromosome from the father, which does not carry the gene for the X-linked condition.
4
Determine the probability of inheritance from a heterozygous mother.
The mother has a 50% chance of passing the affected XX chromosome to any given child, male or female.
During meiosis, the two XX chromosomes segregate randomly into eggs, independently of the fertilizing sperm's sex chromosome.

Anahtar Kavram

X-linked Dominant Inheritance Patterns
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Genetics and Heredity

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