1) imagine a sex-linked dominant disease found on the x-chromosome of humans. if
ID: 202883 • Letter: 1
Question
1) imagine a sex-linked dominant disease found on the x-chromosome of humans. if the offspring of a certain mating pair have a 50% chance of receiving the disease, regardless of gender, which of the following statement is true? explain your choice
The father has the disease
The mother is heterozygous for the disease
The mother is homozygous for the disease
The mother does not have the diseae
2) a young girl is diagnosed with duchenne muscular dystrophy ( x linked recessive) and her mother is pregnant with baby boy. which of the following must be true? explain your choice
Her Father's Father had the disease
Her brother will have the disease
Her father had the disease
Her mother had the disease
Her father's mother was a carrier
Explanation / Answer
1. Option B is correct.
XD = Mutant dominant allele
Xd = WT recessive allele
Parental cross: XDXd X XdY
Progeny: XDXd XDY XdXd XdY
Here, half the males and half the females are affected. As a whole, half the progeny are affected irrespective of their gender.
2. Option C is correct.
Xm = Mutant recessive allele
XM = WT dominant allele
Parental cross: XMXm X XmY
Progeny: XmXm XmY XMXm XMY
Affected daughter = XmXm
She can be affected only when her father is also affected (He must contain the disease-causing allele).
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