Chapter 12 Practice Problems
Name
1)
A man and woman both have normal color vision, but their daughter has red-green color blindness, a sex-linked
recessive trait. The man sues his wife for divorce on grounds of infidelity. Can genetics provide evidence
supporting his case?
2)
Hemophilia in humans is inherited as an X-linked recessive trait. A woman whose father is hemophiliac marries a
man with normal clotting ability. What is the probability that her first child will have hemophilia? Assume that
the woman's mother is homozygous dominant.
4)
In Drosophila melanogaster, the dominant allele for body color is gray and the dominant allele for wings is
normal. The recessive alleles of these two genes result in black body color and vestigial wings respectively. Flies
homozygous for gray body and normal wings were crossed with flies that had black bodies and vestigial wings.
The F1 progeny were then test-crossed, with the following results:
Gray body, normal wings 236
Black body, vestigial wings 253
Gray body, vestigial wings 50
Black body, normal wings 61
What is the recombination frequency?
5)
Draw a chromosome map for genes A, B, C, D, E, and F based on their recombination
frequencies. Be sure to label the shortest map distances.
6)
Great Northwestern Guava plants produce fruit that have thick or thin skins, tart or sweet fruit, and large or
small seeds. Thick skins and large seeds are dominant. You have obtained two of these plants. One has thickskinned fruit with large seeds, and the other has thick-skinned fruit with small seeds. On performing a cross
between these two plants, you obtain the following progeny:
(i)
290 produce thick-skinned with large seeds
(ii)
106 produce thin-skinned with large seeds
(iii)
309 produce thick-skinned with small seeds
(iv)
95 produce thin-skinned with small seeds
Pair
AB
AC
AD
AE
AF
BC
BD
BE
BF
CD
CE
CF
DE
DF
EF
RF%
19
15
10
38
5
33
10
20
24
24
52
10
28
15
43
(a) What are the most likely genotypes of the two plants you started out with?
(b) Perform a chi-square to support or refute an assumption of independent assortment. Be sure to
show the chi-square value and the probability.