Bio93 Discussion Week 7
1. When a dominant allele coexists with a recessive allele in a heterozygote:
a. They do not interact at all
b. The dominant allele prevents expression of the recessive allele
c. The dominant allele prevents transcription of the recessive allele
2. A sexually reproducing plant has a diploid chromosome number of 10. What is the minimum number
of different gametes it can produce based on Mendel’s law of independent assortment?
a. 100
b. 32
d. 10
e. 5
3. Marfan syndrome in humans is caused by an abnormality in fibrillin, a connective tissue protein.
Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, weakened
arterial walls, and ocular problems such as lens dislocation. Which of the following statements about
Marfan syndrome is definitely true?
a. it is recessive
b. it is dominant
c. it is pleiotropic
d. it is epistatic
e. it is polygenic
4. In Drosophila, the mutations wingless (wg) and vestigial (vg) are two different genes that map to the
second chromosome and both result in wings that are smaller than wildtype (+). If a homozygous
wingless mutant fly is mated to a homozygous vestigial mutant, which of the following offspring would
you expect?
a. all wg+ vg+ heterozygotes
b. half wingless and half vestigial mutant flies
c. all homozygous wildtype flies
d. 3:1 wingless to vestigial ratio
e. half mutant and half wildtype flies
5. Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color
vision have a color-blind son. What are the genotypes of the parents?
6. You are provided with a bunch of dividing cells, and you accidentally dump radioactive thymine all
over them. What would happen if a cell replicates in the presence of this radioactive base? Draw the
DNA of the two daughter cells, and label which strand(s) is radioactive.
7. You sequence the genome of a cell and find that 15% of its nucleotides contain adenine. What
percentage of its nucleotides contain guanine?
8. For the nucleotide sequence shown below, draw the complementary strand, labeling as many parts as
possible:
5’ – CGGATCAATTATAGC – 3’
Bonus: circle the part of the sequence that is likely to be an origin of replication. Why?