Zoo/Bot 3333
Genetics
Quiz 2
September 30, 2005
For answers to the quiz, please click here:
Questions 1-2 pertain to the
following. In the figure to
the right, gene r+ encodes a
transcription factor that is
mRNA
required for the transcription
mRNA
a+ gene
of the a+ gene in a certain
product leads to
plant; r mutants are unable to
normal growth
bind to the appropriate site in
DNA to initiate a+ gene mRNA synthesis. The a+ gene is a growth-promoting
factor, and null mutations in this gene lead to slower than normal growth, and a dwarflike phenotype. Both loci are haplosufficient.
1. True or false. One functional r+ gene will allow a plant that is homozygous for the a
gene mutant to have a normal phenotype.
2. Suppose a plant that is heterozygous for the a and r mutations is allowed to selffertilize. What would be the ratio of normal to dwarf plants?
a) all normal; b) 3 normal: 1 dwarf; c) 15 normal: 1 dwarf; d) 9 normal:7 dwarf; e) 13
normal; 3 dwarf.
Questions 3-5 pertain to the chart on the right. In
Labrador retrievers, coat color may be black, brown
(chocolate) or golden. Here are some of the many
possibilities resulting from the matings of dogs of
different coat colors:
3: True or false. The allele responsible for golden coat
color is located at the same genetic locus as the allele for
brown coat color.
4. The pattern of inheritance seen in these matings
indicates that the golden phenotype is an example of:
a) complementary gene action; b) duplicate genes; c) dominant epistasis; d) recessive
epistasis; e) dominant suppression.
5. In the cross shown in (e):
a) the first parent is heterozygous for the brown allele; b) the second parent is
homozygous for the golden allele; c) the second parent is heterozygous for the brown
allele; d) all of the above; e) none of the above.
Questions 6-8 pertain to the following. In Drosophila, Lyra (Ly)
and Stubble (Sb) are dominant mutations located on chromosome
3. A recessive mutation for bright-red eyes is discovered and
also shown to be located on chromosome 3. A female who was
heterozygous for all three mutations was crossed to a male
homozygous for the bright-red (indicated br here) mutation, with
the progeny classes produced at the right:
6. The map distance from the Stubble mutation to the bright-red
mutation is:
a) 3.4 map units; b) 4 map units; c) 13.4 map units; d) 14 map
units; e) 18 map units.
Phenotype
Ly Sb br
Ly + br
Ly + +
+++
+ Sb +
Ly Sb +
+ + br
+ Sb br
Total
Number
404
75
18
422
59
4
2
16
1000
7. The Lyra locus is 19 map units from the bithorax body locus. Using the map on page
132 of your text, which gene maps closest to the bright-red mutation?
a) rosy eyes; b) glass eyes; c) cardinal eyes; d) pink eyes; e) scarlet eyes.
8. True or false: For this particular data set, we see no evidence of interference between
these three genes.
Questions 9 and 10 pertain to the following. The following are ordered tetrad pairs from
a cross between strain cd and ++:
Tetrad Class
1
2
3
4
5
6
7
c+
c+
cd
+d
c+
cd
c+
c+
cd
cd
c+
++
++
+d
+d
++
++
c+
cd
cd
cd
+d
+d
++
+d
+d
++
++
1
17
41
1
5
3
1
9. The distance between the c locus and the centromere is approximately:
a) 7.3 map units; b) 14.5 map units; c) 15.9 map units; d) 20.3 map units; e) 31.8 map
units.
10. The distance between these two genes is approximately:
a) 9 map units; b) 23 map units; c) these genes do not appear to be linked to one another.