Ichthyosis is a recessive sex-linked disorder that causes a person's skin to flake off like fish scales. A normal man and a normal woman produce a child with ichthyosis. This child cannot be female.

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The child must be male because ichthyosis is a recessive sex-linked disorder, which means that it is carried on the X chromosome. A normal man has one X chromosome and one Y chromosome, while a normal woman has two X chromosomes. If the child were female, she would have two X chromosomes, and one of them would have to carry the ichthyosis gene in order for her to have the disorder. However, since the child has ichthyosis and the father is normal, the child must have inherited the ichthyosis gene from the mother. This means that the mother must be a carrier of the ichthyosis gene, and she must have passed the gene on to her son.

Ichthyosis Is a Recessive Sex-Linked Disorder That Causes a Person's