BIOL/PBIO 3333
Genetics
Quiz 2
9/27/13
For the answers to the quiz, click here
1. Which of the following dihybrid x dihybrid ratios show independent assortment?
a) 9:3:3:1; b) 9:7; c) 9:3:4; d) all of the above; e) none of the above.
2. Tribbles are animals that have a sex determination mechanism similar to humans. The
trait marine (m), with short, stiff hair, is recessive to long furry hair (m+), and purple
color (p) is recessive to black color (p+). A purple, furry female is crossed to a black,
marine male. All of the progeny are furry black. If the marine trait was sex linked and the
purple trait was autosomal, which of the following phenotype frequencies would be
expected in the F2 generation? a) 3/8 black furry females; b) 3/16 black marine males; c)
1/8 purple, furry females; d) 1/16 purple marine males; e) all of the above.
Questions 3-4 refer to the following.
In a group of tribbles, you discover three different
eye color phenotypes: red (R), brown (B) and
green (G). To understand the inheritance pattern,
you conduct a number of different crosses
between animals of these phenotypes. The results
are depicted on the right (the phenotypes
segregate independent of sex):
3. True or false. These results indicate that there
are two independently assorting gene loci
involved in these phenotypes.
cross
number
1
2
3
4
5
6
7
8
9
10
parental phenotypes
phenotypes of progeny
RxG
all R
BxG
all B
RxG
1R:1B
BxG
1B: 1G
GxG
all G
RxR
3R: 1B
BxB
all B
RxG
1:R:2G:1B
RxR
9R:3B:4G
RxB
3R:3B:2G
4. If the red parent from cross #3 and the brown parent from #10 are crossed, what
progeny ratios would be produced?
a) 1 R: 1 B; b) all R: c) all B; d) 3 R: 1 B; e) none of the above.
Questions 5-6 pertain to the following: In hobbits, the recessive
genes for non-hairy feet (f), allergy to pipe-weed (p) and poor
appetite (a) are all recessive to the wild type alleles. Females
heterozygous for all three genes were mated to males
homozygous recessive for all traits. The phenotypes of the
recovered progeny are given in the table on the right:
5. The distance, in map units, between the f and a loci is:
a) 2 ; b) 5; c) 16; d) 21; e) these genes are not linked.
6. The coefficient of coincidence for this experiment is:
Phenotype
f+a
+pa
++a
fp+
fpa
+p+
f++
+++
Number of
Progeny
391
81
25
20
2
404
74
3
a) 0.005; b) 0.25; c) 0.625; d) 0.75; e) none of the above.
7. A testcross between an individual who is trihybrid for
three different gene loci (A/a, B/b, C/c) and an individual
homozygous recessive for all three loci yields the
following progeny:
Which of the following are true?
a) the three gene loci are linked and A/a is the middle
gene; b) the A and C genes are located on the same
chromosome and separated by 50 map units; c) the B
locus is located 15 map units from the C locus; d) all of
the above; e) none of the above.
Questions 8-9 pertain to
the data on the right,
showing the ordered tetrad
pairs arising from the
cross between two strains,
cd and ++.
Phenotype
ABC
abc
ABc
AbC
aBC
Abc
aBc
abC
Number of
Progeny
34
40
204
215
41
35
221
210
Tetrad Class
spore pairs
1
cd
cd
++
++
41
2
c+
++
cd
+d
5
3
cd
++
cd
++
3
4
c+
cd
++
+d
17
5
+d
c+
c+
+d
1
6
c+
+d
cd
++
1
8. The distance between the c gene and the centromere is:
a) 5 m.u.; b) 7.3 m.u. ; c) 10 m.u.; d) 14.5 m.u.; e) none of the above.
9. The c gene and the d gene:
a) are on the same side of the centromere, with c closest; b) are on the same side of the
centromere, with d closest; c) are on opposite sides of the centromere, with d closest; d)
are on opposite sides of the centromere, with c closest; e) are on different chromosome
homologs- they are not linked.
10. Mutations in the fibrillin-1 gene:
a) are dominant; b) are pleiotropic; c) can show variable expressivity; d) are located on
chromosome 15; e) all of the above.
7
c+
c+
+d
+d
1