Bio 130 – Quiz March 30
Q. 1 Albinism in humans occurs when both alleles at a locus
produce defective enzymes in the biochemical pathway leading
to melanin. Given that heterozygotes are normally pigmented,
which of the following statements is/are correct?
A. One normal allele produces enough melanin for a normal
phenotype.
B. Each defective allele produces a little bit of melanin.
C. Two normal alleles are needed for normal melanin production.
D. The two alleles are codominant.
E. The amount of sunlight will not affect skin color of heterozygotes.
Q. 2 Imagine a locus with four different alleles for fur color in an
animal. The alleles are named Da, Db, Dc, and Dd. If you crossed
two heterozygotes, DaDb and DcDd, what genotype proportions
would you expect in the offspring?
A.
B.
C.
D.
E.
25% DaDc, 25% DaDd, 25% DbDc, 25% DbDd
50% DaDb, 50% DcDd
25% DaDa, 25% DbDb, 25% DcDc, 25% DdDd
50% DaDc, 50% DbDd
25% DaDb, 25% DcDd, 25% DcDc, 25% DdDd
Q. 3 In geckos spotted skin (S) is dominant to stripey skin (s).
Long tails (T) are dominant to short tails (t). If we cross a
female that is SsTt with a male that is Sstt, what is the chance
that an offspring will have stripey skin and a short tail?
A.
B.
C.
D.
E.
0
½
¼
1/8
1/16
Q. 4 In geckos spotted skin (S) is dominant to stripey skin (s). Long
tails (T) are dominant to short tails (t). If we cross a female that is
SsTt with a male that is Sstt, what is the chance that an offspring
will have spotted skin and a short tail?
A.
B.
C.
D.
E.
0
½
¾
3/8
3/16