BioSc 231
General Genetics
Exam 4
Name __________________________________
Multiple Choice. (3 points each)
1) _____ A base change resulting in a codon specifying an amino acid which is the same as the wild-type polypeptide
A.
B.
C.
D.
Missense
Silent
Nonsense
Frameshift
2) _____ A transversion mutation is one in which
A. A purine substitutes for a purine
B. A pyrimidine substitutes for a pyrimidine
C. A purine substitutes for a pyrimidine
3) _____ A microorganism that cannot grow on minimal medium due to a defect in tryptophan metabolism would be a(n) ___ mutant.
A.
B.
C.
D.
conditional
autotrophic
auxotrophic
prototrophic
4) _____ A bacterial histidine mutant was plated on minimal medium and a single colony grew. The revertant organism that grew
would be described as a(n)
A.
B.
C.
D.
auxotroph
prototroph
syntroph
histroph
5) _____ You decide to sequence the histidine biosynthetic gene of the revertant in the previous questions and discover that the
original mutation is still present. This colony must have been able grow due to a
A.
B.
C.
D.
forward mutation
suppressor mutation
auxotrophic mutation
back mutation
6) _____ A cell is exposed to 5-bromouracil (a thiamine analog that mispairs with guanine) and allowed to undergo a few rounds of
DNA replication. The mutational event caused by this mutagen will be
A.
B.
C.
D.
E.
TA to CG
CG to AT
AT to TA
AT to CG
GC to CG
7) _____ A new E. coli mutant was tested for auxotrophy. The mutant grows on:
minimal medium (M) + Threonine (T) + Alanine (A)
M + T + Cysteine (C)
M+T+A+C
but not on M
or on M + C + A. The mutant requires
A.
B.
C.
D.
threonine
alanine
cysteine
threonine and alanine
8) _____ The _____ test of Luria and Delbruck established that resistant mutations arise prior to the time they were selected
A.
B.
C.
D.
Ames
fluctuation
reversion
substitution
9) _____ Himalayan rabbits have an appearance similar to Siamese cats, in which their body is primarily a light cream color but have
patches or black at their extremities. This coloration is due to a mutation in the gene responsible for black pigmentation. The type of
mutation in this gene is described as
A.
B.
C.
D.
conditional
lethal
somatic
variable
10) _____ When a diploid organism undergoes spontaneous endoreduplication the resulting cells are best described as
A.
B.
C.
D.
polyploid
triploid
aneuploid
trisomic
11) _____ How many different trisomics could be formed in a plant with a diploid number of 10?
A.
B.
C.
D.
E.
1
5
6
10
11
12) _____ E. coli cells were spread on an agar plate, producing 1000 colonies. The colonies are replica plated on four agar plates
containing 10 micrograms per milliliter of the antibiotic tetracycline and one agar plate without antibiotic. All of the colonies are able
to grow on the agar plate without antibiotic but only 3 colonies grew on each of the agar plates containing tetracycline. You notice
that the three colonies that grew on each of the tetracycline plates are in the exact same position on each plate. This demonstrates
A.
B.
C.
D.
E.
that mutations occur in prokaryotes as well as in eukaryotes
that mutations occur in the absence of the selective agent
that in some cases mutations are caused by the selective agent itself
how to screen for environmental mutagens
a direct correlation between the amount of the selective agent used and the number of resistant mutants (one-hit relationship)
13) _____ A human karyotype of 45, XO is indicative of?
A.
B.
C.
D.
Klinefelter's syndrome
Fragile X syndrome
Turner syndrom
Huntungtons chorea
14) _____ A hybrid allotetraploid species (2n = 32) was backcrossed to one of the suspected parents (2n = 16). When the F 1
underwent meiosis, the prophase chromosome configuration was examined. If the guess about the suspected parent is correct, what
would the chromosome configuration look like?
A.
B.
C.
D.
E.
16 pairs
16 pairs and 8 singles
24 singles
8 pairs and 8 singles
32 singles
15) _____Klinefelter syndrome is due to the following karyotype
A.
B.
C.
D.
E.
47, XYY
47, XXY
47, 21+
45, XO
45, YO
16) _____ Polyploid plants found in nature usually have even numbers of chromosome sets because organisms having odd numbers of
chromosome sets
A.
B.
C.
D.
exhibit altered mitosis
exhibit altered growth
have low fertility
are not viable
17) _____ Pollen from one species with a genome represented by (BB) germinates on the stigma of another related species with a
genome represented by (EE) and sexually fertilizes the ovule. Most of the resulting plants are sterile but some of the resulting
offspring undergo chromosome duplication resulting in fertile plants. The genomes of the fertile offspring are best represented
by
A.
B.
C.
D.
E.
BB
EE
BBEE
BEE
BBE
18) _____ In a mammal, no Barr bodies are observed. How many X chromosomes does the organism have?
A.
B.
C.
D.
0
1
2
3
19) _____ Euploidy is
A.
B.
C.
D.
E.
a chromosome number that is not an exact multiple of the haploid number
an example of aneuploidy
a chromosome number that is an exact multiple of the haploid number
the addition of an extra copy of a particular chromosome
the absence of a particular copy of a chromosome
20) _____ When an organism gains one extra copy of a chromosome but not a complete haploid set, the conditions is known as
A.
B.
C.
D.
polyploidy
euploidy
aneuploidy
triploidy
21) _____ Consider a species with a diploid (2n) number of 8 chromosomes. How many chromosomes would be found in a trisomic
body cell?
A.
B.
C.
D.
E.
2
4
5
8
9
Short Answer (variable points each)
(4 pts) Name four different kinds phenotypes resulting from point mutations (i.e. the type of amino acid change that can occur).
(2 pts) Why do calico cats have patches of black and orange fur?
(2 pts) Briefly explain how detecting mutant bacteria using the Ames test is related to the cancer causing potential of chemicals.
(4 pts) A set of Drosophila mutants with various deletions in chromosome 2 was assembled. The deletions in each mutant (a to f) is
diagrammed below (the lines indicate the region that has been deleted)
Regions
1
a
b
c
d
e
f
2
3
4
5
6
7
_________
_________________
_______________
______
___________
_______
normal wings
vestigial wings
vestigial wings
normal wings
vestigial wings
normal wings
A mutation leading to vestigial (short) wings is mapped to chromosome 2. A geneticist crosses a strain with the vestigial allele to each
of the above deletion strains. The phenotype of the offspring of each cross is indicated to the right. In which region of the
chromosome is the gene for normal wings located?
(2 pts) Monoploid plant cells are treated with colchicines to regenerate diploid plant cells. What does colchicine do that leads to
chromosome duplication?
(2 pts) When you expose prototrophic bacteria to a chemical mutagen, you obtain auxotrophic mutants at a certain frequency.
However, when you expose an auxotrophic bacterium to the same chemical mutagen, you obtain protrophic mutants at a much lower
frequency. Why?
(2 pts) Most forms of trisomy in humans are lethal. However, some forms of trisomy such as trisomy 21 are viable but can have
severe complications. Why is trisomy often lethal?
(2 pts) Why are mules, the offspring of a female horse and a male donkey, sterile?
(4 pts) Genes c, e ,g, i, m, n and o are closely linked but their order is unknown. A set of 7 deletions are used to determine the gene
order as revealed by the recessive alleles of each gene which are exposed by each deletion. The genes exposed by each deletion are as
follows:
deletion number
1
2
3
4
5
6
7
gene(s) exposed
o and m
n, o and m
g and e
e
e and n
i, m and o
i and c
What is the order of the genes?
(2 pts) Occasionally, DNA polymerase makes a mistake and incorporates an incorrect base into a newly synthesized DNA strand.
The cell has mechanisms to repair these errors. However, the repair enzymes need to know which DNA strand has the correct base.
In other words, it needs to know which is the original strand. How is this determined?
Short Essays – 5 points each. Five bonus points possible for answering all 3.
Describe one of the two methods discussed in class which can be used to show that certain chemical compounds can cause mutations.
Describe how it was demonstrated that mutations (resistance mutations) can exist in a population of bacteria before the bacteria were
exposed to the selective agent (either the fluctuation test using T1 viruses as the selective agent or the replica plating method using T1
phages or antibiotics as the selective agent)
Write about any topic you studied which you think was not adequately covered in this exam.