Zoo/Bot 3333
Genetics
Quiz 2
September 30, 2011
For the answers to the quiz, click here
1. In the guinea pig, an allelic series is involved in coat color, where C (full color) >ck (sepia) >
cd (cream) > ca (albino). A sepia-colored animal of unsure lineage and a cream-colored guinea
pig from a pure breeding line are crossed, giving rise to progeny that are ½ cream and ½ sepia.
One of these sepia offspring is now crossed to a full-colored guinea pig that had an albino parent.
What fraction of the progeny of this cross would be expected to be cream-colored?
a) none; b) ¼; c) 3/8; d) ½ e) none of the above.
Questions 2-4 pertain to the following:
In tribbles, (males XY, females XX) a series of matings between albino females (all the same
genotype) and brown males (all the same genotype) produced the following results: 96 albino
males and 99 females in the distribution 25 black, 50 brown, and 24 cream.
2. The phenotypes described above can be explained by genetic transmission through how many
independent gene loci?
a) a single gene locus containing an allelic series; b) two gene loci, one containing a sex linked
recessive; c) two gene loci, one showing dominant epistasis; d) three gene loci; e) none of the
above.
3. If a black F1 female tribble is crossed to a parent brown male, which of the following would
be expected?
a) all black offspring; b) only black males and brown females; c) 9 brown females: 3 black
females: 3 black males:1 albino male; d) 2 black females: 2 brown females: 2 albino males: 1
black male: 1 brown male; e) 1 black male: 1 brown female: 1 black males: 1 brown male.
4. True or false. It is impossible to produce a true breeding stock of cream tribbles.
5. A plant of genotype AB/ab is testcrossed to a plant of genotype ab/ab. If the two gene loci are
12 map units apart, what proportion of the progeny are going to be aabb in genotype?
a) 3%; b) 6%; c) 12%; d) 44%; e) none of the above.
In maize, a strain homozygous for two recessive mutations, liguleless (lg) and glossy seedling (gl)
was crossed to another strain homozygous for a dominant allele (B) that puts red pigment into the
stem and leaves. The F1 plant was backcrossed to the homozygous recessive strain, and seeds
from that cross were of the following phenotypes and numbers:
+ lg gl
B++
B lg gl
+++
B lg +
+ + gl
+ lg +
B + gl
172
162
56
48
51
43
6
5
6. The distance between the B and gl loci is:
a) 11.1 map units; b) 18.8 map units; c) 19.3 map units; d 21.2 map units; e) the B and gl loci are
not linked.
7. The coefficient of coincidence for this cross is:
a) 0.041; b) 0.959; c) 0.022; d) 0.49; e) none of the above.
The father of Eldarian, second High King of the Reunited Kingdom, was Aragorn (known by the
hobbits as Strider), guardian of the Shire and member of the Fellowship of the Ring. Eldarian’s
mother was the Elf, Arwen, a descendant of the Elven king, Elrond. An Elf has pointed ears
(determined by allele P), extreme youth and longevity (determined by allele A, leading to
unlimited cell renewal) and lack of facial hair in males (determined by L). All are dominant to
the normal human alleles. The three loci are autosomal, and they are linked as shown in the
following linkage map:
P-------------------------18 m.u.---------------A-------6 m.u. --------L
8. If Eldarian married a human woman, and interference was 0.6, what proportion of their sons
would be expected to have human longevity, but be dominant for the other Elvish phenotypes?
a) 0.0108; b) 0.00216; c) 0.0054; d) 0.0135; e) none of the above.
A Neurospora of genotype ab was crossed to a different mating type that contained ++ alleles for
these two gene loci. 1000 thousand asci were scored, and the data set in the following table was
recovered:
Spore
1
2
3
4
5
6
7
number
ab
a+
ab
ab
ab
ab
a+
1
ab
a+
ab
ab
ab
ab
a+
2
+b
a+
ab
++
++
+b
+b
3
+b
a+
ab
++
++
+b
+b
4
++
+b
++
+b
++
a+
+b
5
++
+b
++
+b
++
a+
+b
6
a+
+b
++
a+
ab
++
a+
7
a+
+b
++
a+
ab
++
a+
8
190
1
779
10
5
10
5
totals
9. The distance from the centromere to gene locus a is approximately:
a) 5.5 map units; b) 7.5 map units, c) 11 map units; d) 22 map units; e) 30 map units.
10. True or false. The b locus is located close to the centromere, approximately 11-12 map units
from the a locus.