NOTE—Questions 1-5 and 9-12 from last year’s exam are on material that will not
be covered on your Exam III . Additional sample questions are provided after
question 40 of this exam.
BIOL. 303
EXAM III
11/17/05
Name_____________________________
------------------------------------------------------------------------------------------------------------------This exam consists of 40 multiple choice questions worth 2.5 points each. On
the separate testing form, please fill-in the single best choice for each question. Be
sure to fill-out your student number and name on the answer sheet. Good luck!
---------------------------------------------------------------------------------------------------------------------1.
When scientists were attempting to determine the features of the genetic code,
Crick and co-workers found that when three base additions or three base deletions
occurred in a single gene, the wild type phenotype was sometimes restored. This
observation supported the hypothesis that
1.
2.
3.
4.
the code is triplet.
AUG is the initiating triplet.
the code is overlapping.
there are three amino acids per base.
2.
In 1964, Nirenberg and Leder used the triplet binding assay to determine specific
codon assignments. A complex of which of the following components was trapped on
the nitrocellulose filter?
1.
2.
3.
4.
3.
ribosomes and DNA
free tRNAs
charged tRNA, RNA triplet, and ribosome
uncharged tRNAs and ribosomes
Which of the following is true?
1. every amino acid is coded for by a single codon.
2. there are more amino acids than there are codons.
3. every codon codes for an amino acid.
4. each codon in a gene codes for no more than one single amino acid.
4.
The genetic code is “degenerate” because
1. there are more codons than amino acids.
2. there are more amino acids than codons.
3. different organisms use different codons to encode the same amino acid.
4. some codons specify more than one amino acid.
5.
What is the name given to the three bases in a messenger RNA that bind to the
anticodon of tRNA to specify an amino acid placement in a protein?
1.
2.
3.
4.
protein
anti-anticodon
cistron
codon
6.
When studying the initiation of transcription, one often finds consensus
sequences located in the region of the DNA where RNA polymerase(s) bind. Which are
common consensus sequences?
1.
2.
3.
4.
7.
CAAT, TATA
GGTTC, TTAT
TTTTAAAA, GGGGCCCC
any trinucleotide repeat
An intron is a section of
1.
2.
3.
4.
protein that is clipped out posttranslationally.
RNA that is removed during RNA processing.
DNA that is removed during DNA processing.
transfer RNA that binds to the anticodon.
8.
Three posttranscriptional modifications often seen in the maturation of mRNA in
eukaryotes are
1.
2.
3.
4.
9.
5'-capping, 3'-poly(A) tail addition, splicing
3'-capping, 5'-poly(A) tail addition, splicing
removal of exons, insertion of introns, capping
5'-poly(A) tail addition, insertion of introns, capping
What is the initiator triplet in both prokaryotes and eukaryotes and what is the
amino acid coded for by this triplet?
1. UAA, no amino acid coded.
2. UAA, methionine.
3. AUG, arginine.
4. AUG, methionine.
10.
Which type of RNA molecule carries an amino acid to the ribosome?
1. tRNA
2. rRNA
3. mRNA
4. siRNA
11.
The term “peptidyl transferase” relates to
1. base additions during mRNA synthesis.
2. peptide bond formation during protein synthesis.
3. elongation factors binding to the large ribosomal subunit.
4. 5' capping of mRNA.
12.
By their experimentation using the Neurospora fungus, Beadle and Tatum were
able to propose the hypothesis that:
1. prototrophs will grow only if provided with nutritional supplements.
2. several different enzymes may be involved in the same step in a biochemical
pathway.
3. the role of a specific gene is to produce a specific enzyme.
4. more than one codon can specify a given amino acid.
13.
What is the term which refers to a contiguous set of bacterial genes which are
under coordinate control?
1. lysogen.
2. prototroph.
3. operon.
4. allosteric.
14.
Which term most appropriately refers to a trans acting regulatory factor?
1.
2.
3.
4.
translation
RNA processing
DNA binding protein
helicase activation
15.
The lac operon
1. is under negative and positive control.
2. is under positive control only.
3. is normally expressed constitutively.
4. is an example of tissue-specific expression.
16.
What is the function of cAMP in regulation of the lac operon?
1. activates a repressor protein
2. activates an activator protein
3. inactivates a repressor protein
4. inactivates an activator protein
17.
When a repressor binds to an operator, what process is affected?
1. Transcription of the operon is prevented.
2. DNA replication of the operon is prevented.
3. mRNA made from the operon cannot be translated.
4. Protein made from the operon does not function.
18.
A mutant E. coli strain, grown under conditions that normally induce the lac
operon, produces high amount of ß-galactosidase. What is a possible genotype of the
cells? (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter;
O = lac operator)
1. lacI+ lacP+ lacO+ lacZ– lacY+ lacA+
2. lacI+ lacP+ lacOc lacZ+ lacY+ lacA+
3. lacI– lacP+ lacO+ lacZ– lacY+ lacA+
4. lacI+ lacP– lacO+ lacZ+ lacY+ lacA+
19.
Consider a bacterial strain that has a mutant lac operator region that cannot bind
repressor. If you were to introduce into this strain a wild type operator region on
an F’ element, the cell would
1. synthesize lactose.
2. display inducible expression of the lac operon.
3. display constitutive expression of the lac operon.
4. probably not catabolize lactose.
20.
With regards to the trp operon,
1. tryptophan is an inducer.
2. tryptophan is a co-repressor.
3. attenuation can halt replication.
4. none of the above.
21.
Under the system of genetic control of the trp operon,
1. when there are high levels of tryptophan in the medium, transcription of the
trp operon occurs at high levels.
2. when there is no tryptophan in the medium, transcription of the trp operon
occurs at high levels.
3. when there are high levels of tryptophan in the medium, transcription of CAP
(CRP) occurs at high levels.
4. when there are high levels of tryptophan in the medium, ribosomes “stall” and
reduce the levels of tryptophan synthesized.
22.
Which of the following clusters of terms applies when addressing enhancers as
elements associated with eukaryotic genetic regulation?
1.
2.
3.
4.
cis-acting, variable orientation, variable position
trans-acting, fixed position, fixed orientation
cis-acting, fixed position, fixed orientation
trans-acting, variable position, fixed orientation
23.
Regarding eukaryotic and prokaryotic genetic regulation, what process seems to
be the most similar between the two?
1.
2.
3.
4.
24.
transcriptional regulation
RNA splicing regulation
intron/exon shuffling
5'-capping regulation
What modification neutralizes the charges on histones and loosens up the
interactions between histones and DNA?
1. phosphorylation
2. methylation
3. acetylation
4. polyadenylation
25.
What is are some functions of eukaryotic transcription factors?
1. They recognize sequences within the enhancer and promoter regions and
activate transcription.
2. They direct the mRNA from the nucleus to the cytoplasm.
3. They initiate binding to the Shine-Dalgarno sequence.
4. They serve as sequences where the RNA polymerase binds
26.
In eukaryotes, mRNA is transcribed by
1. RNA polymerase I
2. RNA polymerase II
3. RNA polymerase III
4. none of the above.
27.
One form of post-translational modification of a protein is
1. removal of introns.
2. shuffling of exons.
3. removal or modification of amino acids.
4. removal of exons.
28.
In eukaryotes, actively transcribed chromatin is
1. DNase insensitive.
2. in a highly condensed form
3. usually DNase sensitive.
4. sometimes referred to as heterochromatin.
29.
The term "chromatin remodeling" refers to
1. alteration of chromatin structure in association with transcription.
2. a process that only bacteria perform since they contain no nucleus.
3. a process that is exclusively associated with transcription by RNA polymerase
III in eukaryotes.
4. alteration in chromatin structure to facilitate loading and translation by
ribosomes and, thus, enhance gene expression.
30.
The phenomenon known as “RNAi” (RNA interference) is used experimentally to
1.
2.
3.
4.
reduce expression of a specific target gene.
reduce transcription rate from a specific gene promoter.
interfere with replication.
enhance gene expression.
31.
Mutant versions of genes that are normally involved in promoting the cell cycle
are known as
1.
2.
3.
4.
tumor suppressors.
proto-oncogenes.
oncogenes.
attenuators.
32.
What is the name of the protein that helps to regulate multiple checkpoints
throughout the cell cycle and is also known as the “guardian of the genome?”
1. p34
2. p102
3. cyclin
4. p53
33.
What are three general mechanisms that may be involved in the conversion of
proto-oncogenes to oncogenes?
1.
2.
3.
4.
point mutations, translocations, overexpression.
inversions, translocations, methylation.
familial, sporadic, phosphorylation.
suppression, tabulation, projection.
34. A person born with an inherited predisposition to cancer usually does not develop
cancer until after
1.
2.
3.
4.
exposure to radiation.
LOH of the inherited mutation.
age 70
Mardis Gras
35.
Most cancer is caused by
1. a single mutation.
2. two mutations.
3. a collection of several mutations that must occur in a specific order
4. a collection of several mutations that can occur in any order.
36.
Regarding the relationship between viruses and cancer, which statement is most
accurate?
1. viruses cause some cancers in animals, but viruses are not associated with
cancer in humans.
2. most human cancers are known to be caused by viruses.
3. viruses are not associated with cancer in animals or humans
4. some human cancers are closely associated with viral infection and some
cancers can possibly be prevented by vaccination against virus.
37.
What is the function of dideoxynucleotides in Sanger DNA sequencing?
1. They act as primers for DNA polymerase.
2. They act as primers for reverse transcriptase.
3. They cut the sequenced DNA at specific sites.
4. They stop synthesis at a specific site, so the base at that site can be
determined.
38.
Which of the following is not needed in order to amplify a DNA fragment by
PCR?
1. a set of primers.
2. knowledge of the complete nucleotide sequence of the fragment to be
amplified.
3. a DNA polymerase.
4. deoxynucleotide triphosphates.
39.
Nucleic acid blotting is widely used in recombinant DNA technology. In a
Southern blot one generally
1. hybridizes filter-bound DNA with a DNA probe.
2. hybridizes filter-bound RNA with a DNA probe.
3. examines amino acid substitutions with radioactive probes.
4. cleaves RNA with restriction endonucleases.
Use the following diagram of a DNA sequencing gel for question 40.
ddATP reaction
ddTTP reaction
ddCTP reaction
ddGTP reaction
40.
What was the sequence of the DNA strand that was synthesized in the
sequencing reaction?
1. 5' GCTAGCA 3'
2. 5' ACGATCG 3'
3. 5' TGCTAGC 3'
4. 5' CGATCGT 3'
That’s all!
41.
A bacterial enzyme that cuts DNA within a short, specific sequence and is used
in many applications by molecular biologists is known as a
1. topoisomerase.
2. restriction enzyme.
3. polymerase.
4. glycosidase.
42.
Based on the most recent analysis of the sequence of the human genome, which
is closest to the estimated number of human genes?
1. 3,000
2. 30,000
3. 100,000
4. 500,000
43.
Sequencing bacterial genomes has revealed that
1. all bacterial genomes consist of a single circular DNA molecule.
2. all bacterial chromosomes are linear DNA molecules.
3. a bacterial genome can consist of more than one DNA molecule, but all
bacterial chromosomes are circular.
4. None of the above
44.
In the process of making a “knockout mouse,” the first genetically altered mouse
that is made is called
1. a chimeric mouse
2. a heterozygous knockout
3. a homozygous knockout
4. Mickey