Zoo/Bot 3333
Genetics
Quiz 1
9/2/11
For answers to the quiz, please click here
1. If you had three dice and threw them, what would be the probability that none of the
three dice would land on a five?
a) 1/6; b) 1/18; c) 125/216; d) 5/6; e) none of the above.
2. True or false. The DNA content (and estimated number of genes) of the mouse and
human genomes is approximately the same.
3. True or false. Although the eyes of fruit flies and the eyes of humans are both lightdetecting organs, they have a completely different developmental history, programmed
by completely different genes.
Questions 4-5 pertain to the following: Assuming independent assortment for all 5 traits
in the cross:
aaBbccddEE x AaBbCcDdEe
4. For these 5 traits, what proportion of the progeny will phenotypically resemble the
first parent (aaBbccddEE) ?
a) 1/16; b) 3/32; c) 1/128; d) 3/256; e) none of the above.
5. For these 5 traits, what proportion of the progeny will phenotypically resemble
neither parent?
a) 1/32; b) 3/32; c) 3/16; d) 13/16; e) none of the above.
6. In a certain species of frog a dihybrid cross is made between the genotypes AaBb
and AaBb. At least on copy of the dominant A allele is required for normal
development; the recessive a allele is homozygous lethal, preventing gastrulation
during embryogenesis. The dominant B allele, however, is also homozygous lethal,
leading to severe skeletal defects and fetal death. Individual heterozygous for B (i.e.
Bb) are viable, however, and have a dwarf phenotype. What will be the ratio of dwarf to
normal frogs in the progeny originating from this cross?
a) all dwarf; b) 3:1; c) 2:1; d) 1:1; e) none of the above.
7. Of the surviving progeny, what fraction would be expected to be genotypically
identical to their parents?
a) ¼; b) 1/3; c) 2/3; d) 2/9; e) none of the above.
The pedigree on the right shows the
pattern of transmission of two rare human
phenotypes- cataract and pituitary
dwarfism. Family members with cataracts
are indicated with a vertical lines in the
symbol (e.g. I-1); those with pituitary
dwarfism, by a horizontal line in the
symbol (e.g. I-2).
8. Which of the following indicates the
most likely inheritance pattern for these
disorders?
a) both are autosomal dominant; b) both
are autosomal recessive; c) cataracts are autosomal dominant and dwarfism is
autosomal recessive; d) dwarfism is autosomal dominant and cataracts are autosomal
recessive; e) unable to predict from the above information.
9. If individuals IV-2 and IV-4 marry, what are the odds that their child will be affected
with one of these rare disorders?
a) 1/9; b) 1/12; c) 1/24; d) 1/36; e) none of the above
10. Tay-Sachs disease is a rare human disease which leads to neuronal degeneration,
and ultimately death. It is caused by a defect in the enzyme hexosaminidase A, and is
inherited as an autosomal recessive. A woman is planning to marry her first cousin, but
the couple discovers that their shared grandfather’s sister died in infancy of the disease.
What is the probability that the first child of this couple will have the disorder,
assuming all those that marry into the family are homozygous for the wild-type allele?
a) zero; b) 1/1024; c) 1/144; d) 1/96; e) none of the above.