exam 5

Question 1

What mRNA is expressed at elevated growth temperatures, leading to transcription of heat shock genes?
a. sigma70
b. rpoH
c. 1S10
d. Cro
e. glmS

Answer 1

b. rpoH

Question 2

The CAP binding site in the lac promoter is the location of positive regulation of gene expression for the operon. How does the binding exert a positive effect?

a. The CAP-CAMP complex prevents the binding of the repressor protein.
b. CAP interacts with Tup-1 to prevent transcription in the presence of Glucose
c. The CAP-CAMP complex alters the structure of the promoter and allows RNA polymerase to bind to it.
d. The CAP-CAMP complex triggers the formation of the DNA loop, which prevents binding of the repressor protein.
e.The CAP-CAMP complex unbends the DNA loop, thereby allowing binding of RNA polymerase.

Answer 2

c. The CAP-CAMP complex alters the structure of the promoter and allows RNA polymerase to bind to it.

Question 3

Which of the following is true of the partial diploid cell below I^s P+ O^c Z- Y+ / I- P+ O+ Z- Y+

a. Beta-galactosidase would be constitutively transcribed and permease would be inducible
b. Beta-galactosidase would be uninducible and permease would be constitutively expressed
c. I was really hoping you wouldn’t ask this one Dr. Trott
d. both Beta-galactosidase and permease would be constitutively expressed
e.Beta-galactosidase would be constitutively transcribed and permease would be non-inducible

Answer 3

b. Beta-galactosidase would be uninducible and permease would be constitutively expressed

Question 4

Which of the following conditions would induce the lytic cycle in Lambda phage infected E. coli cells?
a. Poorly growing bacterial host population
b. Mutating the cl gene in a way that causes its protein product to bind to DNA more strongly
c. Mutating the N protein in a way that prevents its binding to DNA
d. Higher levels of cl than cro in the cell
e. Large number of co-infecting phage

Answer 4

c. Mutating the N protein in a way that prevents its binding to DNA

Question 5

What would happen to the expression of the lac operon a bacterial cell if you mutated the enzyme adenylate cyclase in a way that caused it to make cAMP constitutively?
a. The lactose operon would be non-inducible even in the presence of lactose
b. The lactose operon would be expressed at high levels in response to lactose in the presence and/or absence of glucose
c. The lactose operon would be expressed at high levels in response to lactose but only in the absence of glucose
d. The lactose operon would be non-inducible except for in the presence of glucose
e. The lactose operon would be constitutively expressed even in the absence of lactose

Answer 5

b. The lactose operon would be expressed at high levels in response to lactose in the presence and/or absence of glucose

Question 6

Which of the following statements regarding Nucleotide Excision Repair (NER) and Base Excision Repair (BER) is TRUE?
a. Both NER and BER involve the creation of an apyrimidinic (AP) site. b.
Both NER and BER can be activated by exposure to visible light.
C. Only NER involves the action of DNA ligase to seal nicks in the DNA backbone.
d. Both NER and BER involve the removal of one or more damaged bases by a nuclease.
e. Only NER involves the creation of an apyrimidinic (AP) site

Answer 6

d. Both NER and BER involve the removal of one or more damaged bases by a nuclease.

Question 7

Which of the following features of the trp operon is likely least essential to the process of attenuation?
a. Trp codons near the beginning of the leader sequence
b. The ability of sequences within the leader mRNA to pair with one another
c. The order of the structural genes, E, D, C, B, A
d. Transcription and translation of the leader sequence occur simultaneously.

Answer 7

c. The order of the structural genes, E, D, C, B, A

Question 8

Which of the following spontaneous mutations alters DNA structure/sequence and generally results from strand slippage?
a. Depurination
b. Deamination of cytosine
c. Expansion of trinucleotide repeat sequences
d. Proofreading failures
e. Tautomeric shift that changes the structure of a base

Answer 8

c. Expansion of trinucleotide repeat sequences

Question 9

Translation of the thiMD operon genes in E. coli occurs when..

a. high TPP concentration initiates the riboswitch that leads to intrinsic termination
b. low TPP concentration leads to the formation of an antitermination stem-loop
c. low TPP leads to the formation of a Shine-Dalgarno antisequestor stem loop d. low TPP concentration leads to the formation of a riboswitch to initiate transcription
e. high TPP concentration leads to the formation of an antitermination stem-loop

Answer 9

c. low TPP leads to the formation of a Shine-Dalgarno antisequestor stem loop

Question 10

Which type of DNA damage is repaired by the enzyme photolyase?

a. double-strand breaks
b. apurinic sites
c. alkylation of bases
d. single-strand breaks
e. thymine dimers

Answer 10

e. thymine dimers

Question 11

The purpose of the Ames Test is to
a. Oh man, I forgot to study the Ames test…
b. determine whether histidine has mutagenic effects in S. typhimurium
c. test the mutagenic effects of chemicals
d. determine whether Salmonella typhimurium his- mutants can revert to his+
e. study how the liver affects potential mutagens

Answer 11

c. test the mutagenic effects of chemicals

Question 12

In the bacterial transformation lab, which of the following is most directly responsible for allowing bacteria to grow in the presence of Ampicillin?
a. GFP gene
b. AraC
c. bla gene
d. The presence of Arabinose in the media
e. LB growth media

Answer 12

c. bla gene

Question 13

Ataxia telangiectasia (OMIM 208900) is a human inherited disorder characterized by poor coordination (ataxia), red marks on the face (telangiectasia), increased sensitivity to X-rays and other radiation, and an increased susceptibility to cancer. Recent studies have shown that this disorder occurs as a result of mutation of the ATM gene. ATM is a protein kinase that is activated in response to DNA damage and then activates other proteins that cause cell cycle arrest and/or apoptosis. Which of the following explains why DNA repair mechanisms cannot correct this problem.
a. A loss of ATM function cannot be overcome by the action of DNA repair pathways because enzymes for this process become blocked
b. A loss of ATM function cannot be overcome by the action of DNA repair pathways because this mutation is permanent.
C. A loss of ATM function cannot be overcome by the action of DNA repair pathways because cells enter S-phase before there is enough time for DNA repair.
d. A loss of ATM function cannot be overcome by the action of DNA repair pathways because the cell starts apoptosis.
e. A loss of ATM means you can no longer access your money.

Answer 13

C. A loss of ATM function cannot be overcome by the action of DNA repair pathways because cells enter S-phase before there is enough time for DNA repair.

Question 14

Which of the following is a consequence of mutational inactivation of both p53 alleles in a cell?
a. Relative instability of the non-functional protein
b. Reduction of p21 synthesis
c. decreased rates of certain types of cancer
d. Programmed cell death (apoptosis of the cell
e. A reduction in kinase activity of the cyclin-Cdk complex

Answer 14

b. Reduction of p21 synthesis

Question 15

If the UGG codons in Region 1 of trpL were changed to AGG codons, what effect would this have on expression of the trp operon?

a. The operon would be regulated by arginine levels; high levels of arginine would attenuate expression of trp genes.
b. The operon would be constitutively expressed.
c. The operon would be regulated by tryptophan, but attenuation would be triggered at higher levels of tryptophan than in wild type.
d. The operon would be regulated by tryptophan, but attenuation would be triggered at lower levels of tryptophan than in wild type.
e. The operon would never be expressed

Answer 15

a. The operon would be regulated by arginine levels; high levels of arginine would attenuate expression of trp genes.

Question 16

Which of the following occurs as a result of an abundance of tryptophan in E. coli?
a. The leader sequence is not transcribed.
b. The 5 trp genes (TrA - TrE) are transcribed, but not translated.
c. The 5 trp genes (TrA - TrE) are not transcribed.
d. The leader sequence is duplicated
e. Stalling of the ribosome at trp codons in the leader sequence

Answer 16

c. The 5 trp genes (TrA - TrE) are not transcribed.

Question 17

To use RFLP analysis to detect a SNP, the SNP must ________.
a. occur in heterozygous form
b. occur within a restriction enzyme recognition sequence
c. cause disease
d. occur within a the sequence of a transposon
e. be present in at least 11% of the population

Answer 17

b. occur within a restriction enzyme recognition sequence

Question 18

In mismatch repair in E, coli. The MutH/L/S system uses nearby 5’-GATC-3’ sequences. Which of the following modifications is common on this sequence?
a. Ethylation on the Thymine
b. None of these are correct
c. Methylation on the Adenine
d. Methylation on the Guanine
e. apurinic sites on the Guanine or Adenine

Answer 18

c. Methylation on the Adenine

Question 19

Two different mutations are identified in a haploid strain of yeast:
The first prevents the synthesis of adenine by a nonsense mutation of the ade-1 gene. In this mutation, a base-pair substitution changes a tryptophan codon (UGG) to a stop codon (UGA).
The second affects one of several duplicate tRNA genes. This base-pair substitution mutation changes the anticodon sequence of a tRNAT from 3’-ACC- 5’ to 3’-ACU- 5’.
What term would best be used to describe the second mutation?

a. non-sense mutation
b. intragenic reversion
c. suppressor mutation
d. forward mutation
e. reverse mutation

Answer 19

c. suppressor mutation

Question 20

It has been observed that diseases caused by repeat expansions are the result of trinucleotide repeats rather than smaller or larger repeat lengths. If NON-trinucleotide repeat expansions were present in the coding region of a gene, which type of mutation would you expect to be the most likely?

a. terminal deletion
b. nonsense
c. missense
d. silent
e. frameshift

Answer 20

e. frameshift

Question 21

Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?

a. a frameshift deletion (2 bases) at the beginning of the gene
b. a base substitution at the beginning of the gene
c. a base substitution at the end of the gene
d. a frameshift insertion near the polyadenylation site of the gene
e. an insertion of three nucleotides near the end of gene

Answer 21

a. a frameshift deletion (2 bases) at the beginning of the gene

Question 22

The spectrum shown is typical of dsDNA. (The wavelength scale has been removed for the purpose of this question.) What wavelength do we expect the maximum absorbence for a pure sample of DNA (non-contaminated)?
a. 230
b. 320
c. 280
d. 260
e. 240

Answer 22

d. 260

Question 23

Which transposable element in bacteria lacks insertion sequences?
a. I don’t know yet….:)
b. Non-composite transposons
c. Ty elements
d. Try elements
e. Composite transposons

Answer 23

b. Non-composite transposons

Question 24

What type of damage results in an apurinic (AP) site?
a. Breaking the covalent bond at the 5’ carbon of deoxyribose in a purine.
b. Replacing the hydrogen atom at the 5 carbon with a CH3 (methyl) group.
c. Breaking the covalent bond at the 4’ carbon of deoxyribose in a pyrimidine.
d. Breaking the covalent bond at the 4’ carbon of deoxyribose in a pyrimidine.
e. Breaking the covalent bond at the 1’ carbon of deoxyribose in a purine.

Answer 24

e. Breaking the covalent bond at the 1’ carbon of deoxyribose in a purine.

Question 25

______ is an inhibitor of apoptosis in healthy cells that can be directly inhibited by ______ in cells with DNA damage.

Answer 25

BCL2
BAX

Question 26

a. BAX, p21
b. BCL2, p21
c. RecA, RuvB
d. BCL2, ВАX
e. p21, p53

Answer 26

d. BCL2, ВАX

Question 27

Match the lac operon genotypes with the correct phenotypes, in each case basal transcription is assumed where possible (2 points each)

a. I+ P+ O+ Z+ Y+

b. I^s P+ O + Z+ Y-

c. I+ P+ O^c Z- Y+

d. I- P+ O+ Z+ Y+

e. I+ P+ O+ Z- Y+

___ is lac- and the genes are constitutively transcribed.

___ is lac+ and the genes are constitutively transcribed.

___ is lac- and the genes are not transcribed.

___ is lac- and the genes are inducibly transcribed.

___ is lac+ and the genes are inducibly transcribed.

Answer 27

c. I+ P+ O^c Z- Y+

d. I- P+ O+ Z+ Y+

b. I^s P+ O + Z+ Y-

e. I+ P+ O+ Z- Y+

a. I+ P+ O+ Z+ Y+

Question 28

_________ are molecules that have the same composition and general arrangement but a slight difference in bonding and placement of a hydrogen. (2 points)

Answer 28

tautomers