Name_________________________
Final Exam Biol 212 General Genetics
Fall 2002 (140 points)
Please show your work for full credit. Note that there are population genetics
formulas, a Chi-square table, and a genetic code table on the last two pages of the exam,
for your use. The first part of the exam (#1-28) consists of multiple choice questions, to
be answered on the scantron sheets provided, using a number two pencil. The last three
questions on the exam (#29-31) are problems or short answer questions to be answered in
the spaces provided.
Multiple Choice: Select the one best answer (4 points each)
Part I: Exam 3 questions
1. Tay-Sachs disease is inherited as an autosomal recessive disorder. In a certain large
eastern European population, the frequency of Tay Sachs disease is 1 percent. If the
population is assumed to be in Hardy-Weinberg equilibrium with respect to Tay-Sachs,
what is the frequency of the allele that causes Tay-Sachs?
a. 0.01
b. 0.1
c. 0.9
d. 0.81
2.
a.
b.
c.
d.
e.
A partial diploid of genotype I-P+O+Z+/I+P+O+Z- will show
Inducible production of repressor
Inducible production of -galactosidase
Constituitive production of –galactosidase
No production of –galactosidase
Constituitive production of lactose
3.
a.
b.
c.
d.
The only viable monosomy in humans is
XO, Turner's syndrome
YO, Male androgeny
monosomy 21
XYY
4. If natural selection acts to remove individuals with a trait determined by a
homozygous recessive genotype (fitness=0.6), the long range tendency in the population
will be toward
a. fixation of the A allele and extinction of the a allele
b. fixation of the a allele and extinction of the A allele
c. Hardy-Weinberg equilibrium
d. A balanced polymorphism
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5. The mutation causing the recessive disease allele for sickle-cell anemia removes one
MstII restriction site from the globin gene so that a probe, instead of hybridizing to two
fragments of 1.1 kb and 0.2 kb, hybridizes to one 1.3-kb fragment. For two parents to
have a 25 percent chance of a child with sickle-cell anemia
a.
They must both show only fragments of 1.1 and 0.2 kb.
b.
They must both show fragments of 1.3 and 0.2 kb.
c.
One must show only a 1.1- and the other only a 0.2-kb fragment.
d.
One must show a 1.3- and the other a 1.1- and a 0.2-kb fragment.
e.
They must both show all three types of fragments.
6.
A reciprocal translocation in a wild species of strawberry was discovered. The
normal gene arrangement on the chromosomes was:
abcdef and mnop
The translocation gave rise to chromosomes
mndef and abcop
The reciprocal translocation heterozygote can be diagrammed as shown in the
table below:
Chromosome arrangement
abcdef
mnop
abcop
mndef
chromosome designation (N=normal,
T=translocation)
N1
N2
T1
T2
Which chromosomes (use above designations) must separate from one another at
anaphase I to form viable meiotic products?
a.
b.
c.
d.
e.
7.
a.
b.
c.
d.
N1 separates from N2, T1, and T2.
N1 and T1 separate from N2 and T2.
N2 and T1 separate from N1 and T2.
N1 and N2 separate from T1 and T2.
T1 separates from T2, N1, and N2.
Which of the following is not being used as a vector in gene therapy protocols?
adenovirus
adeno-associated virus (AAV)
bacteriophage lambda
retrovirus
2
8.
a.
b.
c.
d.
The human genome
refers to the entire genetic make-up of human beings
contains a lot of repetitive DNA sequences of unknown function
has at least 30,000-40,000 genes, based on the draft sequence
all of the above are correct
9. A wild-type chromosome can be represented as ABC · DEFGH, and from this a
chromosomal aberration arises that can be represented ABC · DGFEH. This is known as
a. Deletion
b.Translocation
c. Duplication
d. Paracentric inversion
10. The sequence on DNA that lac repressor binds is
a. the promoter
b. the operator
c. the permease gene
d. the I gene
11. Features of eukaryotic pre-mRNAs usually absent in prokaryotic mRNAs include
a. their introns must be removed by splicing
b. a 5' cap and 3' poly (A) tail are added
c. they are usually polycistronic
d. both a and b are correct
e. all of the above
12. In a human population, the genotype frequencies at one locus are 0.5 AA, 0.4 Aa and
0.1 aa. The frequency of the A allele is
a. 0.20
b. 0.32
c. 0.50
d. 0.70
13. VNTRs can be used in DNA fingerprinting because
a. all individuals have the same number of tandem repeats
b. most individuals will have different numbers of tandem repeats
c. the expression of every gene is tested on a single slide
d. known genes that cause genetic diseases are tested
14. Alleles for the genetic disorder, sickle cell anemia provide a selective advantage in
equatorial climates where malaria frequently occurs. This is an example of
a. mutation
b. heterozygote superiority
c. genetic drift
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d. directional selection
Part II: Cumulative questions
15. Two genes are separated by 20 map units on the chromosome. Assuming no
interference, from this one can infer that
a. the recombination frequency for the two genes is 2%.
b. the recombination frequency for the two genes is 10%.
c. the recombination frequency for the two genes is 20%.
d. The genes are assorting independently.
16. The following pedigree shows a human hereditary trait
Is the trait most likely inherited as an
a. autosomal dominant
b. autosomal recessive
c. X-linked dominant
d. X-linked recessive
17. The chromosomal make-up of an individual is its
a. karyotype
b. gamete
c. polyploidy
d. tetrad
18. Which of the following is not an assumption of the Hardy-Weinberg equilibrium?
a. No new mutation.
b. No natural selection.
c. No immigration
d. Non-random mating.
19. The term phenotype describes the
a. specific combination of alleles in a cell
b. fundamental unit of heredity
c. physical location of a gene on a chromosome
d. outward appearance of some characteristic in an individual
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20. A protein fragment has the following sequence NH2-Pro-Met-Phe-Tyr-Cys-COOH.
An mRNA that could be translated to give this protein (5’ ---> 3’) would be:
a. GCAAUAGAACAUGGG
b. CCCAUGUUCUAUUGC
c. CCCATGTTCTATTGC
d. CGTTATCTTGTACCC
e. GCAATAGAACATGGG
21. A sequence of DNA that is labeled with 32P and used to detect a particular gene of
interest in a Southern Blot is called ____________.
a. DNA clone
b. DNA library
c. DNA probe
d. gene map
22. A corn plant known to be hybrid for three linked genes is testcrossed. The progeny
phenotypes and frequencies are
a+c
+b+
++c
ab+
a++
+bc
+++
abc
20
10
368
375
45
50
2
4
The order of the three genes on the chromosome is
a. a—b—c
b. b—a—c
c. a—c—b
d. c—b—a
23. In order to grow, an E. coli leu- mutant (unable to synthesize the amino acid leucine)
must be provided with
a. minimal medium
b. minimal medium containing streptomycin
c. minimal medium containing proline
d. minimal medium containing leucine
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24. In a mating of an Hfr strain that is a+b+c+strs to an F- strain that is a-b-c-strr, the
prototrophic markers were transferred as follows: a+ after 5 min, b+ after 15 min and c+
after 2 min. Therefore the order of the genes and the F factor (F) on the chromosome in
the Hfr strain was:
a. F--a--b--c
b. F--c--b--a
c. F--b--a--c
d. F--c--a--b
25. If genes for two traits showing simple dominance are unlinked and assorting
independently, a cross between two individuals which are heterozygous for both traits
should result in
a. a 9:3:4 ratio of phenotypes
b. a 9:3:3:1 ratio of phenotypes
c. a 3:1 ratio of phenotypes
d. a 9:3:3:1 ratio of genotypes
26. The probability that two individuals who are heterozygous for an autosomal recessive
trait will produce three out of three affected children is
a. 1/4
b. 3/4
c. 1/16
d. 1/64
27. If two individuals AB/ab and ab/ab are crossed and produce an F1 generation, which
of the following genotypes in the offspring would be considered recombinants?
a. AB/ab
b. ab/ab
c. Ab/ab
d. none of the above
28. (Bonus question) The plasmid vector pUC18 has a gene for ampicillin resistance
(AmpR) and the gene encoding β-galactosidase (lac Z+). The Lac Z gene is cut with a
restriction enzyme and donor DNA treated with the same enzyme is added. After ligation
of the foreign DNA into the lac Z gene, what genotype needs to be selected to identify
recombinants?
a. AmpRlacZ+
b. AmpRlacZc. AmpSlacZ+
d. AmpSlacZ-
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Problems and short answer: Show your work for full credit
29. (10 points) Select one of the following genetic diseases (or any other disease you are
familiar with that is due to a single gene defect). Outline what you know about the
disease. For full credit, discuss most or all of the following points in your answer.
A. Describe the symptoms of the disease.
B. How is the disease inherited? Is it recessive or dominant, X-linked or autosomal?
C. Identify the gene that is altered in the disease.
D. Explain how knowledge of mutations in the protein coding region help account
for aspects of the disease.
E. Identify possible ways of diagnosing or treating the disease.
Phenylketonuria
Sickle cell anemia
Cystic fibrosis
Muscular dystrophy
Huntington's disease
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30. (12 pts.) Resistance to HIV virus infection is determined by the chemokine receptor
gene, CCR5. The receptor enables HIV virus to cross the plasma membrane of particular
T lymphocytes, a necessary step for an HIV infection to progress. The resistance
mutation is determined by a deletion of 32 bp (32) with the coding region for the
receptor.
a. Suggest why the 32 deletion in the receptor gene results in a resistance phenotype
when present in homozygous recessive individuals.
(b) The normal (dominant) CCR5 allele will be symbolized by A, and the recessive 32
mutant allele will be designated a. The CCR532 is much more common in Caucasian
populations than among other groups. In a population of 715 Chinese individuals tested
for CCR5 alleles, the following genotypes were found:
AA
699
Aa
16
aa
0
Test (using the Chi-squared test) whether the genotypic frequencies conform to a
Hardy-Weinberg distribution. Note that there is only one degree of freedom because the
three genotypic classes are completely specified by two allelic frequencies.
genotype
AA
obs
exp
obs-exp
d2
d2/exp
___________________________________________________________
Aa_______________________________________________________________
aa________________________________________________________________
X2 = _______
Degrees of freedom = 1
X2 critical value at 0.05 probability = _________
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(d) Would you accept or reject your hypothesis that the population is in Hardy-Weinberg
equilibrium with respect to the CCR5 alleles?
31. (10 points) Diagram the first phase of meiosis (meiosis I) in the following meiotic
precursor cell. Clearly indicate important stages and events (2n = 4 chromosomes)
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Hardy Weinberg Equilibrium is defined by
p2 + 2pq + q2
Where p2 = AA
2pq = Aa or heterozygote
q2 = aa or recessive trait
Genetic code
Chi-square table
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