Gene Mapping Practice
1. The crossover frequency between genes E and F is 6%, between E and G is 10% and between F and G
is 4%. Construct a map of these genes.
2. In 1911, Thomas Hunt Morgan collected the following crossover gene frequencies while studying
Drosophila. Bar-shaped eyes are indicated by the B allele, and carnation eyes are indicated by the
allele C. Fused veins on wings (FV) and scalloped wings (S) are located on the same chromosomes.
Gene Combinations
FV/B
FV/C
B/C
B/S
FV/S
C/S
Recombination Frequency
2.5%
3.0%
5.5%
5.5%
8.0%
11.0%
3. For a series of experiments, a linkage group composed of genes W, X, Y and Z was found to show the
following gene combinations. (All recombinations are expressed per 100 fertilized eggs). Construct a
gene map.
Genes
W
X
Y
Z
W
–
5
7
8
X
5
–
2
3
Y
7
2
–
1
Z
8
3
1
–
Challenge Question:
4. Five traits found in Drosophila are yellow body color (y), white eye color (w), vermilion eye color
(v), miniature wing (m) and rudimentary wing (r). Given the following crossover frequencies,
construct a genetic map.
Genes
y&w
v&m
v&r
v&w
v&y
w&m
y&m
w&r
Crossover Frequency
2.2%
3.0%
26.6%
30.0%
32.2%
33.0%
35.2%
56.6%
Linked Gene Punnett Squares Challenge
1. If having freckles (F) and tongue rolling (D) are on the same chromosome. A man who is
heterozygous for both traits with F and D on one chromosome and f and d on the other chromosome
and a woman who has the same chromosome make up are about to have a baby.
a. What is the chance that the baby will not have freckles but will be able to roll its tongue?
b. Assume the same characteristics as above, but this time, freckles and tongue rolling are NOT
on the same chromosomes. Now, what is the chance that the baby will not have freckles but will
be able to roll its tongue?