Multiple Choice
In a pedigree showing inheritance of a sex-linked recessive trait, which of the following patterns is most likely to be observed?
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2. Mendel's Laws of Inheritance
Sex-Linked Genes
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If a trait is X-linked recessive, which individuals are most likely to express the trait?
A
Males who inherit one copy of the recessive allele
B
Females who inherit one copy of the recessive allele
C
Both males and females equally, regardless of genotype
D
Only females who inherit two copies of the dominant allele
Verified step by step guidance1
Understand that X-linked recessive traits are associated with genes located on the X chromosome, and their expression depends on the number of recessive alleles present on the X chromosomes.
Recall that males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). This difference affects how X-linked traits are expressed.
Recognize that males only need one copy of the recessive allele on their single X chromosome to express the trait, because they do not have a second X chromosome that could carry a dominant allele to mask the recessive one.
Understand that females need two copies of the recessive allele (one on each X chromosome) to express the trait, since having one dominant allele on one X chromosome will mask the recessive allele on the other.
Conclude that males who inherit one copy of the recessive allele are most likely to express the X-linked recessive trait, while females must inherit two copies to express it.
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