When X-linked traits are recessive, females will express the traits only if they are _____ for the recessive allele.

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This is because females only have two X chromosomes, while males have one X and one Y chromosome. Therefore, if a female has one X chromosome with the recessive allele and one X chromosome with the dominant allele (heterozygous), she will not express the trait. However, if a female has both X chromosomes with the recessive allele (homozygous), she will express the trait.

When X-Linked Traits Are Recessive, Females Will Express the Traits