1.

What information can be deduced from a pedigree? Select the TWOanswers that are correct.

	the probability of a female being a carrier of an X-linkedallele
	how an X-linked trait is passed down over generations
	the probability of a parent or grandparent being infertile
	how autosomal traits contribute to X-linked traits
	the probability that Y-chromosome analysis will provepaternity

2.

A grandfather has an X-linked disease. His wife does not havethe disease and she is not a carrier for it. What is theprobability that their daughter's sons will have the disease?

	0%
	75%
	100%
	50%
	25%

3.

Why are X-linked traits more commonly expressed in males thanin females? Select the TWO answers that are correct.

	Females have only one X chromosome, whereas males havetwo.
	Males have an X and a Y chromosome, and females have two Ychromosomes.
	Males have two X chromosomes, making them twice as likely tohave the phenotype.
	Males have only one X chromosome, whereas females havetwo.
	Females have two X chromosomes, so one can mask the effects ofthe other.

4.

Can males be carriers of an X-linked trait?

	Yes, because males have one copy of the X chromosome
	No, because males have two copies of the X chromosome
	No, because males have only one copy of the X chromosome
	No, because females do not pass X-linked traits to maleoffspring
	Yes, because the Y chromosome also codes for the trait