Multiple Choice
If a woman is heterozygous for a recessive sex-linked allele and her husband has the dominant allele, which one of the following is true about the probabilities for their children?
2243
views
13. Mendelian Genetics
Sex-Linked Inheritance
Multiple Choice
Duchenne muscular dystrophy is caused by a sex-linked recessive allele. Its victims are almost invariably boys, who usually die before the age of 20. Why is this disorder almost never seen in girls?
A
Sex-linked traits are never seen in girls.
B
The allele is carried on the Y chromosome.
C
Nondisjunction occurs in males but not in females.
D
A sex-linked allele cannot be passed from mother to daughter.
E
To express an X-linked recessive allele, a female must have two copies of the allele, one of which is contributed by the father.
Verified step by step guidance1
Understand that Duchenne muscular dystrophy is a sex-linked recessive disorder, meaning the gene causing the disorder is located on the X chromosome.
Recognize that males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).
For a female to express a recessive X-linked disorder, she must inherit two copies of the recessive allele, one from each parent.
In the case of Duchenne muscular dystrophy, a female would need to inherit the recessive allele from her mother (who could be a carrier) and her father (who would have the disorder).
Since males with Duchenne muscular dystrophy often do not survive to reproductive age, it is rare for a female to inherit the disorder from her father, making the condition almost never seen in girls.
Related Videos
Related Practice
