Zoo/Bot 3333
Genetics
Quiz 3
4/3/09
For the answers to the quiz, click here:
1. In Burkitt’s Lymphoma:
a) a hybrid MYC protein is produced as a result of a translocation; b) a proto-oncogene is transferred into
the immunoglobulin gene cluster and expressed at high levels; c) the drug Gleevec has been approved for
treating this disorder; d) all of the above; e) none of the above.
Questions 2-3 pertain to the following: Three strains of Drosophila (Bravo, X-ray, and Zorro) are obtained
that are homozygous for three variant forms of a particular chromosome. When examined in salivary gland
polytene chromosome spreads, all chromosomes have the same number of bands in all three strains. When
genetic mapping is performed in the Bravo strain, the following map is obtained (distances in map units).
a
b
5.8
c
6.2
d
3.2
e
5.7
f
4.4
Bravo and X-ray flies are now mated to form Bravo/X-ray
F1 progeny, and Bravo flies are also mated with Zorro
flies to form Bravo/Zorro Fj progeny. In subsequent
crosses, the genetic distances on the right were found to
separate the various genes in the hybrids:
g
7.1
h
3.2
Gene Intervals
a-b
b-c
c-d
d-e
e-f
f-g
g-h
Bravo/X-ray
5.8
6.2
0.2
<0.1
<0.1
0.65
3.2
Bravo/Zorro
5.8
0.7
<0.1
<0.1
<0.1
0.7
3.2
2. Which of the following is the most likely explanation
for the differences between the strains?
a) reciprocal translocations have occurred, giving rise to
balanced translocation heterozygotes; b) inversions have occurred suppressing crossing over; c) deletions
have occurred in two different regions of the chromosome; d) duplications have occurred in two different
regions of the chromosome; e) a chromosomal deletion has occurred in one strain and a duplication has
occurred in the other strain.
3. In the original X-ray homozygous strain, which of the following statements are true?
a) a and c are closer than in the Bravo strain; b) c and d are closer than in the Bravo strain; c) c and f are
closer than in the Zorro strain; d) all of the above; e) none of the above.
4. Deletions can be used to determine the orientation of genes on a chromosome. A series of 5 deletions
"uncovered" the following recessive mutations in deletion heterozygotes, allowing them to show
pseudodominance (see text 496 3e):
deletion 1:
deletion 2:
deletion 3:
deletion 4:
deletion 5:
o, p, n
n, p
k, l, o
m, n, p
l, n, o
Which of the following gene orders is consistent with a deletion map of this area?
a) npoklm; b) ponkol; c) klopnm; d) klonpm; e) more than one solution is possible.
5. During ascus formation in Neurospora, any ascospore with a chromosomal deletion dies and appears
white in color. How many ascospores of the eight spores in the ascus would be white if the octad came
from a cross of a wild-type strain with a strain of the opposite mating type carrying a reciprocal
translocation, and an adjacent-1 segregation occurred with no crossovers between translocated
chromosomes?
a) none; b) 2; c) 4; d) 6; e) 8.
Questions 6-7 pertain to the following. An Hfr strain of the genotype a+b+c+d+strs is mated with a
female strain of the genotype a−b−c−d−strr. At various times the culture is disrupted in a blender to
separate the mating pairs. The cells are then plated on agar of the following four agar types (see table
below, right), where nutrient A allows the growth of a− auxotrophs, nutrient B allows for the growth of b−
autxotrophs, etc. As indicated, all types contain streptomycin (Str). A (+) indicates the presence of the
nutrient or drug, a (-) indicates its absence.
Agar Type Str A B C D
Timings of Samples Number of Colonies of Agar of Type
+
+ − + +
1
+
+ + +
2
−
1
2
3
4
+
+
+ + −
3
0
0
0
0
0
+
+ + − +
4
2.5
0
4
0
0
5
5
60
0
0
7.5
60
132
0
0
10
98
220
0
0
12.5
127
315
0
6
15
153
370
0
67
17.5
170
398
4
104
20
190
414
35
125
25
205
416
40
138
30
210
420
42
140
35
215
425
48
142
The table above shows the number of colonies on each type of agar for samples taken at various times after
the samples are mixed:
6. From the gene closest to the origin of replication, the order of the genes is:
a) a b c d; b) b a c d; c) c a b d; d) d c b a; e) none of the above
7. True or false. On the basis of this data, gene b is closer to a than it is to d.
8. In a cross between an Hfr that has the genotype x+y+z+ and an F– that is x–y–z–, the x
x+y+z+ 220
gene is known to be transferred later than y and z. To determine the order of y and z with
x+y–z– 60
respect to x, x+ exconjugants are selected and screen for their y and z phenotypes. The
x+y–z+ 18
results of these tests are listed in the chart on the right:
x+y+z– 0
These results indicate:
a) that z is between x and y; b) that the distance between x and z is much smaller than the distance between
x and y; c) that z is closer to the F factor origin than y; d) all of the above; e) none of the above.
Questions 9-10 pertain to the following You have infected E. coli cells
with two strains of T4 virus. One strain is minute (m), rapid lysis (r), and
turbid (tu); the other is wild type for all three markers. The lytic products
of this infection are plated and classified. The resulting 10,342 plaques
were distributed among eight genotypes, as follows:
m r tu
+++
mr+
m + tu
3467
3729
853
162
m++
+ r tu
+r+
+ + tu
9. From this data set, the order of the gene loci is:
a) m r tu; b) r m tu; c) m tu r; d) it is impossible to calculate from this data set.
10. On the basis of this data set, a map distance between the m and r genes can be calculated as:
a) 12.8 map units; b) 20.8 map units; c) 27.2 map units; d) 46.5 map units; e) none of the above.
520
474
172
965