Between which two genes would you expect the highest frequency of recombination?
A) A and W
B) W and E
C) E and G
D) A and E
E) A and G

A and G

In a series of mapping experiments, the recombination frequencies for four different linked
genes of Drosophila were determined as shown in Figure 12.2. What is the order of these genes
on a chromosome map?
A) rb-cn-vg-b
B) vg-b-rb-cn
C) cn-rb-b-vg
D) b-rb-cn-vg
E) vg-cn-b-rb

b-rb-cn-vg

Which of the following are the phenotypes of the parents in this cross?
A) 2 and 5
B) 1 and 6
C) 4 and 8
D) 3 and 7
E) 1 and 2

4 and 8

In which progeny phenotypes has there been recombination between genes A and B?
A) 1, 2, 5, and 6
B) 1, 3, 6, and 7
C) 2, 4, 5, and 8
D) 2, 3, 5, and 7

1, 2, 5, and 6

If recombination frequency is equal to distance in map units, what is the approximate distance
between genes A and B?
A) 1.5 map units
B) 3 map units
C) 6 map units
D) 15 map units
E) 30 map units

3 map units

What is the greatest benefit of having used a testcross for this experiment?
A) The homozygous recessive parents are obvious to the naked eye.
B) The homozygous parents are the only ones whose crossovers make a difference.
C) Progeny can be scored by their phenotypes alone.
D) All of the progeny will be heterozygous.
E) The homozygous recessive parents will be unable to cross over.

Progeny can be scored by their phenotypes alone.

The greatest distance among the three genes is between a and c. What does this mean?
A) Gene c is between a and b.
B) Genes are in the order: a–b–c.
C) Gene a is not recombining with c.
D) Gene a is between b and c.
E) Distance a–b is equal to distance a–c.

Genes are in the order: a–b–c.

How many of their daughters might be expected to be color-blind dwarfs?
A) all
B) none
C) half
D) one out of four
E) three out of four

none

What proportion of their sons would be color-blind and of normal height?
A) none
B) half
C) one out of four
D) three out of four
E) all

half

They have a daughter who is a dwarf with normal color vision. What is the probability that
she is heterozygous for both genes?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%

100%