Download BioSc 231 Exam 2 2008

BioSc 231
General Genetics
Exam 2
Name __________________________________
Multiple Choice. (4 points each)
____ In a complementation test the number of complementation groups indicates
A.
B.
C.
D.
E.
the number of genes required for a specific phenotype
the penetrance of a phenotype
the number of phenotypes for a gene
the number of chromosomes in an organism
the quantity of gene product required for a phenotype
_____ A plant of genotype C D/C D is crossed to c d/ c d and the resulting F1 testcrossed to c d/c d. If the
genes are unlinked, the percentage of c D recombinants will be
A.
B.
C.
D.
E.
10%
25%
30%
40%
50%
_____ In Drosophila the alleles for brown and for scarlet eyes (resulting from two independent genes) interact so
that the double homozygous recessive is white. A pure-breeding brown (BBss) and pure breeding scarlet (bbSS)
(P generation) are crossed. What proportion of the F2 will be white?
A.
B.
C.
D.
E.
1/4
3/4
1/16
7/16
9/16
_____ The Arabidospis genes gr and een are linked, 30 map units apart. If a plant gr+ een/gr een+ is
testcrossed, what proportion of the progeny will be gr een/gr een?
A.
B.
C.
D.
0.03
0.15
0.20
0.50
_____ In humans, the unlinked dominant alleles, P and B, are both required for normal development of the
cochlea and the auditory nerve, respectively. Either of the recessive alleles, p and b, can result in deafness due
to impairment of these essential parts of the ear. Which of the following sets of parents would produce all
hearing children?
A.
B.
C.
D.
PPbb x ppBB
PpBb x PpBb
Ppbb x PpBb
PpBb x PPBb
_____ In sweet peas, the two allelic pairs C, c and P, p are known to affect pigment formation in the flowers.
The dominants, C and P, are both necessary for colored flowers - absence of either results in white. A dihybrid
plant with colored flowers is crossed to a white one which is heterozygous at the “c” locus. What are the
genotypes of these two plants?
A.
B.
C.
D.
E.
CcPp and Ccpp
CCPP and Ccpp
ccpp and Ccpp
CcPp and ccpp
CcPp and ccPp
_____ Assume that an additional allelic pair in sweet peas also affects pigment formation in addition to the
genes mentioned in the previous question. The presence of the dominant R allele is required for red flowers and
the recessive r allele produces yellow flowers. Which of the following genotypes would result in red flowers?
A.
B.
C.
D.
E.
CcPpRr
CcppRR
CcPPrr
ccPPRR
CcppRR
_____ In a complementation test
A.
B.
C.
D.
mutations that complement are allelic
mutations that complement belong to the same complementation group
mutations that complement are in two different genes required for the wild-type phenotype
mutations that are allelic are required for complementation
_____ A person who has type AB blood has
A.
B.
C.
D.
A antigens on the cell surface
B antigens on the cell surface
both A and B antigens on the cell surface
no surface antigens
_____ In crossing over
A.
B.
C.
D.
Genetic exchange occurs before chromosome replication
The probability of its occurrence decreases with increasing distance between the genes exchanged
Occurs more frequently between two loci very close together
The reciprocal exchange between homologous chromosomes is random
_____ A dihybrid cross results in a phenotypic ratio of 12:3:1. This type of ratio most likely results from
A.
B.
C.
D.
E.
incomplete dominance
co-dominance
epistasis
co-penetrance
variable penetrance
Short Answer. (variable points)
Two-point testcrosses revealed the following map results:
br__________ir 9 map units
ir___________cs 5 map units
A. Draw the two possible maps for these loci. (8)
B. What other cross would resolve the two possible maps and what are the possible outcomes of that
cross? (4)
Compound Tested
Mutant
(8) The table to the right shows the results of a series of
experiments to determine the sequence of intermediates in a
biochemical pathway. 4 independent auxotrophic mutants
which all require compound E (an amino acid) as a nutritional
supplement were analyzed with 4 compounds that are
precursors in the synthesis of compound E. Each mutant was
grown on a minimal medium supplemented with each of the
indicated compounds. + indicates growth that is supported by
the indicated precursor. Using the diagram below, show the
order of the intermediates in the pathway and indicate which
step in the pathway is catalyzed by each mutant by placing the
letter representing the appropriate compound in each box and
the number of the appropriate mutant in each circle.
A
B
C
D
E
1
--
--
--
--
+
2
+
+
--
+
+
3
--
+
--
--
+
4
+
+
--
--
+
(8) In pumpkins, jack-o-lantern shaped fruit (o) is recessive to round shaped fruit (o+). Branching vines (s) is
recessive to simple vines (s+). In the P generation, plants from two different pure-breeding lines are crossed.
One variety bears round fruit and has simple vines. The other variety has jack-o-lantern fruits and branched
vines. The resulting F1 plants were testcrossed and the following 240 progeny were obtained:
72
48
54
66
- round, simple
- jack-o-lantern, simple
- round, branched
- jack-o-lantern, branched
Calculate the chi-square and P values based on the prediction that the genes are not linked. (chart is on the last
page)
(12) In corn, the genes m, s and t are linked. The data given below summarize the result of 1000 offspring from
a three-point testcross. From the data, construct a map showing the genes in the correct order and indicating the
distances between each pair of genes.
m+
m
m
m+
m+
m
m
m+
s+
s
s+
s
s
s+
s
s+
t+
t
t
t+
t
t+
t+
t
310
295
77
70
119
108
12
9
(12) Based on the complementation data below, A) how many complementation groups exist, and B) which
mutations belong to each group? (+ = complementation, -- = no complementation)
Mutation
Mutation
1
2
3
4
5
6
7
8
9
1
--
2
+
--
3
--
+
--
4
+
+
+
--
5
+
+
+
--
--
6
+
--
+
+
+
--
7
--
+
--
+
+
+
--
8
+
+
+
+
+
+
+
--
9
+
+
+
+
+
+
+
--
--
10
+
--
+
+
+
--
+
+
+
10
--
Bonus Question (5 pts) An Arabidopsis thaliana flowering mutation has been generated in the Columbia (Col)
line. The mutant line was then crossed with a wild-type Landsberg erectus (Ler) line to generate the F1
generation. The F1 generation was allowed to self to produce the F2 generation. F2 plants that displayed the
mutant phenotype were assayed using the CAPS system to identify a molecular marker that is linked to the
mutant flowering gene. Two markers from each of the five Arabidopsis thaliana chromosomes were tested.
The results of those tests were as follows.
Marker Name
Chromosome
# with Ler
Markers
# with Col
Markers
m 235
m 305
1 top
1 bottom
43
11
51
59
PhylB/hy3
m 429
2 top
2 bottom
38
39
36
29
g 4711
BGL1
3 top
3 bottom
29
20
21
30
GA1
AG
4 top
4 bottom
44
28
38
24
r 89998
DFR
5 top
5 bottom
41
50
45
34
Which marker is linked to the
flowering mutation?