Answer:
Option D
Explanation:
Options for the question
A) The Y chromosome is slower to mature than the X chromosome.
B) Replication of the X chromosome occurs more often in males.
C) Male hormones cause the expression of X-linked traits.
D) Males only have one copy of the X chromosome
Given-
Duchenne muscular dystrophy (DMD) is an X-linked recessive condition which means it will occur in male even if they have one diseased X gene. While females will have this disease only when they have two diseased X gene
Hence, in most of the cases women with only one diseased X chromosome act as carrier and show normal traits.
Let us assume X is normal gene and X' is the diseased gene then
Genotype of normal father will be - XY
Genotype of carrier mother will be - XX'
Now if these two mates, following offspring will be produced
XY * XX'
XX, XX', XY, X'Y
So the male with X'Y will have DMD
Hence, option D is correct
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