Question

Which allele combination is used to represent a female who has a heterozygous sex-linked trait

Answer 1

The allele combination representing a heterozygous female for an X-linked trait is XAXa, where she carries one dominant and one recessive allele, making her a carrier for the trait.

Step-by-step explanation:

The allele combination used to represent a female who has a heterozygous sex-linked trait is XAXa. In this context, one allele is dominant (XA) and the other is recessive (Xa). Females possess two X chromosomes, therefore, a female with one normal (dominant) allele and one mutation (recessive) allele for a given sex-linked trait is considered a carrier. This means she can possibly pass on the recessive allele to her offspring. For instance, in humans, X-linked disorders such as hemophilia and certain forms of color blindness are disproportionately observed in males because they have only one X chromosome (XY), thus one recessive allele (Xa) causes them to express the trait. Females (XX), on the other hand, must inherit recessive alleles from both parents to express the trait. If they inherit only one such allele, they do not usually show the trait but can still pass it to the next generation.

Answer 2

Let's look at the trait for colourblindness which is an X linked trait. Knowing that females have the sex chromosome compliments of XX. And the alleles for being colour blind is denoted as c, and the allele for normal vision is C.

The allelic combination used to represent a female who has a heterozygous sex linked trait, in this case colourblindness is X^C X^c. Only females can carry the allele for colourblindness and not be affected, she is a carrier for this disease.