Question

7.) Haemophilia is an X-linked recessive disorder. If a male haemophiliac mates with a normal (non-haemophiliac) homozygous woman, would the progeny be affected?

a. All males would be carriers. All females would be normal.

b. All males would be normal. Half of the females would be carriers and half of the females would have haemophilia.

c. All males would be normal. All females would be carriers.

d. Half of each sex would be normal and half of each sex would have haemophilia.

e. Half of the males would be normal and half of the males would have haemophilia. All females would be carriers.

12. In general, the frequency with which crossing over occurs between two linked genes depends on what?

a. the phase of meiosis in which the crossing over occurs

b. how far apart they are on the chromosome

c. whether the genes are on the X or some other chromosome

d. whether the genes are dominant or recessive

e. the characters the genes code for

16. Use the following information to answer the questions below.
Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg).
If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the following offspring would you expect?

a. 1/2 bent and vestigial to 1/2 normal

b. 1/2 bent and 1/2 vestigial flies

c. 3/4 bent to 1/4 vestigial ratio

d. all +bt +vg heterozygotes

e. all homozygous + flies

25. The term hemizygous refers to

a. X-linked characteristics expressed in mammalian males.

b. incomplete dominance of phenotypic traits.

c. having two different alleles on the loci of polyploidal species.

d. X-linked characteristics in mammalian females resulting from Barr body silencing.

e. autosomal characteristics in diploid populations.

29. Which of these descriptions of the behaviour of chromosomes during meiosis explains Mendel’s law of independent assortment?

a. Crossing over causes the alleles to switch between chromosomes.

b. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.

c. Sister chromatids separate during anaphase II.

d. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

Answer 1

7. Hemophilia is an X-linked recessive disorder. Let's suppose that the genotype of the hemophilic male is "X^hY" and that of the normal female is "XX".

A cross between them would produce progeny in the following ratio:

1 normal son: 1 normal heterozygous daughter

	Xh	Y
X	XhX Normal but carrier daughter	XY normal son
X	XhX normal but carrier daughter	XY normal son

Answer: c. All males would be normal. All females would be carriers.