Zoo/Bot 3333
Genetics
Quiz 1
1/28/10
For the answers to the quiz, click here
1. Two independently assorting genes, A and B, each possess two alleles, and in both loci
one allele exhibits complete dominance over its recessive counterpart. If plants with the
indicated genotypes were allowed to self-fertilize, which would produce the greatest
number of phenotypic classes among the progeny?
a) Aabb; b) AaBB; c) AaBb; d) AABb; e) all these crosses would produce the same
number of phenotypic classes.
2. In some genetically engineered corn plants, the dominant allele (BT) produces a
protein that is lethal to certain flying insect pests that eat the corn plants. If the corn plant
is heterozygous for BT and the farmer collects self-fertilized corn for next year's crop,
what proportion of those plants would be toxic to insects?
a) all plants; b) 1/4; c) 1/3; d) 1/2; e) 3/4.
Two true-breeding varieties were crossed: a tomato with oblong, yellow fruit was crossed
with a plant with round, red fruit. The F1 plants were inbred (self-fertilized) to generate
the following F2:
Oblong red: 58
Oblong yellow: 180
Round red: 19:
Round yellow: 61
3. The phenotype of the F1 generation would be:
a) oblong, red; b) oblong yellow; c) round red; d) round yellow; e) it is impossible to tell
from this data.
Questions 4-6 pertain to the following:
Consider the following cross, for 5 independently assorting genes showing complete
dominance:
aaBbCcDDEe x AaBbccDdEe
4. What fraction of the progeny of this cross will have a genotype identical to the first
parent (i.e., individual aaBbCcDDEe)?
a) 1/64; b) 1/32; c) 1/4; d) 3/4; e) none of the above.
5. What fraction of the progeny of this cross will have a phenotype identical to the first
parent?
a) 1/64; b) 1/32; c) 1/4; d) 3/64; e) none of the above.
6. What fraction of the progeny of this cross will have a phenotype different from
either parent?
a) 9/64; b) 9/16; c) 23/32; d) 55/64; e) none of the above.
Questions 7-8 pertain to the following.
In Hungarian Horntails, twenty females from a true-breeding black strain were mated
with one grey male of unknown origin. The progeny contained 61 black and 56 grey
progeny.
7. True or false. The black phenotype is dominant in Hungarian Horntails.
8. In Hungarian Horntails, shiny scales (S) are dominant to dull scales (s), red eyes (R)
are dominant to blue eyes (r), and bismuth breath (B) is dominant to sulfur (b) breath. A
shiny-scaled, red-eyed, sulfur-breathed female is mated to a shiny-scaled, red-eyed,
bismuth-breathed male and the following progeny are produced: 10 shiny-scaled, redeyed, bismuth-breathed; 4 dull-scaled, red-eyed, bismuth-breathed; 1 dull-scaled, blueeyed, bismuth-breathed; 3 shiny-scaled, blue-eyed, bismuth-breathed.
The genotypes of the two parents are:
a) SsRRBb x SsRrBb; b) SsRrbb x SsRrBb; c) SsRrbb x SsRRBb; d) SsRrbb x SsRrBB; e)
more than one of these genotypes is possible for this cross.
Questions 9-10 pertain to the following: Brad and Janet become acquainted at a college
social. Their friendship blossoms and they are considering marriage. They know,
however, that there is a history of cystic fibrosis in both families, a disease that is
inherited as a recessive disorder. Brad has a brother who has the disorder, and Janet's
maternal grandfather had a brother and sister who died of the disease.
9. Given their pedigree history, what are the chances that Brad and Janet could have a
child with this disorder?
a) 1/64; b) 1/48; c) 1/36; d) 1/9; e) none of the above.
10. Suppose that Janet learns that her mother's sister has just had a child with cystic
fibrosis (i.e. Janet’s first cousin). The odds that Janet might now have an affected child
are:
a) 1/64; b) 1/48; c) 1/36; d) 1/9; e) none of the above.