Sample Questions to help you prepare for Exam II, which is scheduled for October 20, 2005.
Your real exam will consist of 40 multiple choice questions.
Answers are boldface and underlined. If you have questions, please let me know.
1.
In bacterial conjugation
1. genetic material is transferred in a unidirectional fashion.
2. an F-factor is transferred from an F- strain to an F+ strain.
3. bacteria do not have to physically contact each other for genetic exchange to occur.
4. DNA is transferred through a phage.
2.
In the formation of an Hfr strain of bacteria
1. an F element integrates into the chromosome of a bacterial cell.
2. an F element pops out of the chromosome of a bacterial cell.
3. an F' element is transferred between bacteria.
4. the Hfr strain that forms is a merozygote.
3.
One bacterial Hfr strain transfers genes in the order A--B--C--D--> while a second Hfr
strain transfers genes in the order B--C--D--A-->. The most likely explanation for this is that
1. one strain actually carries an F' element and is a merozygote.
2. the F factor integrated at the same site but in opposite orientations in the two strains.
3. the F factor integrated at different sites and in opposite orientations in the two strains.
4. the F factor integrated at different sites but in the same orientation in the two
strains.
4.
A Barr body is
1. a gene on the X chromosome that is responsible for female development.
2. a patch of cells that has a phenotype different from surrounding cells because of
variable X inactivation.
3. an inactivated X chromosome, visible in the nucleus of a cell from a female
mammal.
4. an extra X chromosome in a cell that is the result of nondisjunction.
5.
What is the expected number of Barr bodies in an individual with the karyotype
XYYY?
1. 0
2. 1
3. 2
4. 3
6.
The genotype XXYY produces a
1. female in Drosophila and a female in humans.
2. female in Drosophila and a male in humans.
3. male in Drosophila and a male in humans.
4. male in Drosophila and a female in humans.
7.
A somatic cell from a person with a trisomy contains a total of how many chromosomes?
1. 46
2. 138
3.
3
4. 47
8.
Familial Down syndrome is caused by:
1. a centric fusion.
2. position effect.
3. nondisjunction.
4. genomic imprinting.
9.
A balanced translocation
1. leads to the condition of “semisterility” even in the absence of any crossing-over.
2. leads to semisterility only if a crossover occurs between the translocated
chromosomes during meiosis.
3. greatly increases the chances of nondisjunction.
4. has no consequence since the genetic material is still balanced.
10. Chromosomal inversions can bring about phenotypic changes. This is best explained by the
phenomenon known as:
1. polyploidy.
2. genetic deletion.
3. position effect.
4. aneuploidy.
11
The genetic material of most living things is
1. deoxyribonucleic acid.
2. ribonucleic acid.
3. RNA.
4. polysaccharide.
12.
The basic structure of a nucleotide includes the following components:
1. amino acids.
2. base, sugar, phosphate.
3. phosphorous and sulfate.
4. all of the above.
13.
A difference between DNA and RNA is that
1. DNA has one less oxygen on each ribose.
2. RNA is genetic material.
3. only DNA is involved in the expression of genetic information.
4. none of the above.
14.
Griffith's classic experiments with mice and Diplococcus pneumoniae
1. demonstrated that DNA is the genetic material.
2. demonstrated that the genetic material is not protein.
3. led to the discovery of the "transforming principle."
4. all of the above.
15.
Which of the following clusters of terms accurately describes DNA as it is generally
viewed to exist in prokaryotes and eukaryotes?
1. Double-stranded, parallel, (A+T)/(C+G)= variable, (A+G)/(C+T)=1.0
2. Single-stranded, antiparallel, (A+T)/(C+G)=1.0, (A+G)/C+T)=1.0
3. Double-stranded, antiparallel, (A+T)/(C+G)=variable, (A+G)/(C+T)=1.0
4. Double-stranded, antiparallel, (A+T)/C+G)=1.0, (A+G)/(C+T)=variable
16.
The AIDS virus, like other retroviruses,
1. has a genome made of DNA.
2. uses reverse transcriptase to convert RNA to DNA.
3. infects only bacteria.
4. is a free-living organism.
17.
Which of the following is a purine?
1. adenine.
2. cytosine.
3. thymine.
4. none of the above.
18.
Which one of the following is part of the Watson-Crick model for DNA?
1. DNA is triple-stranded.
2. the DNA helix is left-handed.
3. DNA consists of two strands of deoxynucleotides with the same polarity.
4. the number of purines equals the number of pyrimidines.
19.
In DNA, each nitrogenous base is directly covalently attached to
1. a phosphate group.
2. a deoxyribose.
3. a ribose.
4. none of the above.
20.
The two strands of a DNA helix are held together (to each other) by
1. covalent bonds.
2. hydrogen bonds.
3. phosphodiester bonds.
4. glycosidic bonds.
21.
If one strand of a short DNA fragment has the sequence 5'-TTTTTTTT-3' then the other
strand of DNA has the sequence
1. 5'-GGGGGGGG-3'
2. 5'-CCCCCCCC-3'
3. 3'-GGGGGGGG-5'
4. 5'-AAAAAAAA-3'
22.
In DNA reassociation experiments, the reassociation of complementary strands of DNA is
plotted as a function of:
1. time.
2. concentration.
3. concentration multiplied by time.
4. molecular weight.
23.
The value of Cot0.5 for the genomic DNA of a prokaryote is directly related to the
1. number of chromosomes.
2. amount of repetitive DNA in the genome.
3. size of the genome.
4. size of the nucleus.
24.
Which statement is true?
1. most naturally occurring genomic DNA has free ends and is thus not subject to
supercoiling.
2. most naturally occurring circular DNA is negatively supercoiled.
3. the linking number of circular DNA can be changed without breaking a strand.
4. none of the above.
25.
Which of the following is NOT an example of middle repetitive DNA?
1. SINES
2. LINES
3. satellites
4. VNTRs
26.
Satellite sequences are usually found in
1. the centromeric region.
2. the coding region of genes.
3. the introns of genes.
4. bacterial genomes.
27.
The so-called "C-value paradox" says that
1. eukaryotes seem to have too little DNA.
2. prokaryotes seem to have too much DNA.
3. prokaryotes seem to have too little DNA.
4. there is a lot of DNA in eukaryotes that has no known function.
28.
In E. coli bacteria, which terms accurately reflect the nature of replication of the genome?
1. bidirectional and fixed point of initiation.
2. unidirectional and conservative.
3. unidirectional and fixed point of initiation.
4. multirepliconic.
29.
In the Meselson-Stahl experiment, what was the density distribution of the isolated DNA
molecules two generations after shifting bacteria from "heavy" to "light" growth medium?
1. 100% of the molecules were of heavy density.
2. 50% were of heavy density, 50% were intermediate density.
3. 100% were of intermediate density.
4. 50% were of light density, 50% were intermediate density.
30.
The discontinuous aspect of replication of DNA is caused by
1. polymerase slippage.
2. the 5' to 3' polarity restriction.
3. trinucleotide repeats.
4. topoisomerases cutting the DNA in a random fashion.
31.
The enzyme that appears to be inappropriately expressed in cancer cells and helps to
maintain the very ends of eukaryotic chromosomes is called
1. topoisomerase.
2. ligase.
3. telomerase.
4. terminase.
32.
The fact that there is a problem maintaining the very ends of eukaryotic chromosomes
during replication has to do with
1. the fact that eukaryotic chromosomes are linear.
2. the inability of DNA polymerases to initiate synthesis without a primer.
3. the restriction that DNA synthesis must occur in a 5' to 3' direction.
4. all of the above. (Note—I previously had the wrong answer marked for this question)
33.
During replication of DNA, strand elongation proceeds
1. in a 5' to 3' direction on the leading strand, but in a 3' to 5' direction on the
lagging strand.
2. in a 3' to 5' direction on the leading strand, but in a 5' to 3' direction on the
lagging strand.
3. in a 5' to 3' direction on both the leading and lagging strands.
4. in a 3' to 5' direction on both the leading and lagging strands.
34.
With regard to eukaryotic chromatin, when one visualizes "beads-on-a-string" each bead
is actually a
1. gene.
2. histone.
3. nucleosome particle.
4. 30 nanometer fiber.
35.
In eukaryotic chromatin, the next highest level of organization above "beads-on-a-string"
is
1. the solenoid.
2. chromatin loops.
3. the nuclear matrix.
4. the metaphase chromosome.
36.
In Luria and Delbruck's classic experiments to distinguish between "spontaneous" versus
"adaptive" mutation,
1. evidence for spontaneous mutation was produced.
2. evidence for adaptive mutation was produced.
3. evidence that DNA is the genetic material was produced.
4. all of the above.
37.
A class of mutations which results in multiple contiguous amino acid changes in proteins
is likely to be the following:
1. frameshift.
2. base analogue.
3. transversion.
4. transition.
38.
Which statement is true?
1. DNA damage and mutation are the same thing.
2. DNA damage is defined as permanent change in the nucleotide sequence.
3. although DNA damage doesn't necessarily lead to mutation, when a mutation does
occur it is always caused by DNA damage.
4. DNA damage can lead to mutation, but doesn't always.
39.
An organism that is deficient in the biosynthesis of a particular important nutrient is
called a(n)
1. prototroph.
2. auxotroph.
3. nutritroph.
4. dead organism.
40.
A tautomeric shift
1. is typically induced by high-energy radiation.
2. occurs only in prokaryotes.
3. can lead to a transversion mutation.
4. can produce a transition mutation.
41.
The "abnormal" tautomeric form of guanine hydrogen bonds well with
1. the abnormal form of adenine.
2. the normal form of guanine.
3. the normal form of cytosine.
4. the normal form of thymine.
42.
In mammals, DNA double-strand breaks may be repaired by
1. mismatch repair.
2. base excision repair.
3. nucleotide excision repair.
4. nonhomologous end-joining
43.
Thymine dimers may be repaired by
1. photoreactivation and excision repair in humans.
2. excision repair but not by photoreactivation in humans
3. oxidative damage.
4. telomerase.
44.
Regarding the SOS response in bacteria:
1. it induces death.
2. if it is defective, it could contribute to the development of cancer
3. it allows bacteria to survive damage by ultraviolet light but the cost is an
increased mutation rate.
4. it prevents mutations that might otherwise be induced by ultraviolet light.
45.
A rare disease is being passed along in a certain family with the unusual property that the
age of onset of this disease appears to be getting earlier and earlier with each successive
generation. The disease is most likely caused by a
1. transversion.
2. centric fusion.
3. dynamic mutation.
4. recessive allele.
46.
The simplest type of transposable elements in bacteria are known as
1. transposons.
2. insertion sequences.
3. Ds elements.
4. Ty elements.