Question

How many unique gamete types are made by a white-eyed male Drosophila?

	a.	2
	b.	4
	c.	3
	d.	1

A man who carries an X-linked allele will pass it on to ______________

	a.	all of his daughters
	b.	all of his sons
	c.	half of his daughters
	d.	all of his sons

Genetic exchange between 2 homologous chromosomes is called

	a.	crossing over
	b.	pleiotropy
	c.	segregation
	d.	chromosome pairing
	e.	independent assortment

Red-green color blindness is a sex-linked recessive traits in humans. Two people with normal color vision have a color blind son. What are the genotypes of the parents?

	a.	XCXc and XCY
	b.	XcXc and XcY
	c.	XcXc and XCY
	d.	XCXC and XcY
	e.	XCXC and XCY

In mice, apricot eyes is recessive to black eyes. Tail length is governed by another gene, linked to the eye color gene. Long tails is dominant to short tails. To determine the distance between the two genes, a double heterozygote is mated in a testcross and the classes of progeny produced were as follows:

Apricot eyes, Long tails 33

Apricot eyes, Short tails             20

Black eyes, Long tails                17

Black eyes, Short tails                30

Determine the map distance between the two genes

	a.	63 map units
	b.	59%
	c.	37 map units
	d.	50%

In mice, apricot eyes is recessive to black eyes. Tail length is governed by another gene, linked to the eye color gene. Long tails is dominant to short tails. To determine the distance between the two genes, a double heterozygote is mated in a testcross and the classes of progeny produced were as follows:

Apricot eyes, Long tails 33

Apricot eyes, Short tails             20

Black eyes, Long tails                17

Black eyes, Short tails                30

Determine whether the heterozygous parent is in the cis or trans arrangement.

	a.	Cis
	b.	Trans

Answer 1

Answer:

1). D. 1

Explanation:

White eye is X-linked recessive trait. It has XwXw genotype; hence it produces only one type of gametes, Xw.

2). A). All of his daughters

Explanation:

All the daughters have two X-chromosomes. Among two, one will get one X-chromosome from her mother and one X-chromosome from the father.

All sons will get only one X-chromosome from his mother only.

3). A). Crossing over

4). A). XCXc and XCY

Explanation:

XCXc (normal female) x (normal male) XCY –Parents

	XC	Y
XC	XCXC (normal daughter)	XCY (normal son)
Xc	XCXc (normal daughter)	XcY (color-blind son)

5). C). 37 map units

Explanation:

Always recombinant progeny are in less number than parental combinations in linkage problems.

Recombination frequency = (no. of recombinants / total progeny)100

= (20+17 / 100)100 = 37%

Recombination frequency (%) = Distance between genes (mu)

37% = 37 map units

6). B). Trans