BCH 405 Exam 3

Which one of the following factors significantly contributes to the ability of eukaryotic cells to complete DNA replication during the short window of time offered by S (synthesis) phase of mitosis?

A. The next round of replication begins before the cell exits S phase.

B. Eukaryotic DNA polymerases have dramatically increased processivity compared to DNA polymerases in organisms with smaller genomes.

C. Multiple origins of replication are used per chromosome.

D. Origins of replication can initiate again after they have been replicated and before mitosis.

C

Dam methylase plays a role in mismatch repair in E. coli. Which of the following statements is true if Dam methylase is absent?

A. There would be no effect on DNA repair.

B. The newly synthesized daughter strand containing the incorrect base and the parental strand will both be unmethylated and, therefore, either strand can serve as the template strand for mismatch repair.

C. All DNA would remain methylated and therefore either strand can serve as the template strand for mismatch repair.

D. Replication will halt

B

Which of the following is an example of a "suicide enzyme"?

A. helicase

B. DNA photolyase

C. dam methylase

D. O6 methyl-guanine transferase

D

Bacteria have developed a system that ensures termination will occur within a restricted terminus region. How is this achieved?

A. By a combination of a DNA motif called the ter sequence, and a termination protein (tus) that recognizes ter sites and binds to them tightly.

B. By the presence of oriC site

C. By the clockwise fork

D. By formation of a catenated DNA molecule

A

SOS repair in prokaryotes involves:

A. Proteolytic activity that activates a specialized DNA polymerase.

B. An error -prone DNA polymerase that can process across unusual structures.

C. Switching DNA pol III holoenzyme for DNA pol V.

D. Coping with damaged DNA but not necessarily repairing the damage.

E. All of the above are true.

E

Which of the following statements about transposon target site duplications is NOT true?

A. They are generated during recombination.

B. They are recognition sequences for transposases.

C. They result from the transposase-mediated strand transfer reaction.

D.They are organized as direct repeats

B

For poly-A retrotransposons, where does cDNA formation occur?

A. In the nucleus

B. In the cytoplasm.

C. In the cytoplasm, but only if reverse transcriptase "out competes" ribosomes for the RNA.

D. At the nuclear pore because that is where the transposase localizes.

A

What are the main differences between replication and transcription?

A. Strand melting is transient in transcription

B. Unlike DNA, RNA does not remain H-bonded to template

C. RNA Pol does not need a primer

D. All of the above

D

Which transcription factor hydrolyzes ATP to force open promoter complex formation in E. coli?

A. TFIIH

B. eIF5b

C. Pribnow box

D. PAP

E. Prokaryotic initiation does not require ATP hydrolysis to form the open promoter complex

E

In prokaryotes, strong promoters can stimulate higher transcription levels (high expression) by:

A. Recruiting histone acetyltransferase to destabilize histone binding

B. Reducing interactions between the non-template strand and σ

C. Attracting proteins that destabilize H bonding near the -35 box

D. Binding the α CTD of RNA polymerase to upstream promoter (UP element)

D

If the mutation has a negligible effect on the function of a gene, it is known as a

A. Silent mutation

B. Frame shift mutation

C. Substitution mutation

D. Insertion mutation

A

The most fundamental components of NHEJ are:

A. Exonuclease and ligase.

B. Artemis

C. Ku70 and Ku80

D. Phosphokinases

C

Which of the following process generates a new copy of the transposable element at a new location of DNA?

A. Homologous genetic recombination

B. Site specific recombination

C. Non-homologous recombination

D. Replicative recombination

D

Which of the following process occurs in regions where no large -scale sequence similarity is apparent?

A. Homologous genetic recombination

B. Site specific recombination

C. Non-homologous recombination

D. Replicative recombination

C

What are the two families of conservative site specific recombinases?

A. Alanine and phenylalanine

B. Threonine and valine

C. Arginine and lysine

D. Serine and tyrosine

D

Transcription occurs along a ____ template forming an mRNA in the ____ direction.

A. 5' to 3'; 5' to 3'

B. 5' to 3'; 3' to 5'

C. 3' to 5'; 5' to 3'

D. 3' to 5'; 3' to 5'

C

DNA glycosylases are responsible for base excision repair by:

A. Addition of correct base

B. Addition of correct nucleotide

C. Removal of incorrect base

D. Removal of phosphodiester bond

C

Photolyase enzyme involved in the photoreactivation can remove...........

A. UV induces double strand breaks

B. UV induced thymine dimers

C. Mismatches in DNA

D. Single strand breaks in DNA

B

What are the main differences between replication and transcription?

A. Strand melting is transient in transcription

B. Unlike DNA, RNA does not remain H-bonded to template

C. RNA Pol does not need a primer

D. All of the above

D

The complex of RNA polymerase, DNA template and new RNA

A. transcript is called

B. transcription bubble

C. replication bubble

D. translation bubble

E. none of these

A

In bacterial promoters, which of the following describes the 'Pribnow box'?

A. The 5' untranslated region

B. The -10 box

C. The -35 box

D. The termination sequence

B

In mismatch repair mechanism, which of the following protein recognizes DNA mismatches in the genomic DNA?

A. MutH

B. MutS

C. MutL

D. UvrD

B

Which of the following binds to ssDNA and does not code for an enzyme having both helicase and nuclease activity?

A. Rec-A

B. Rec-B

C. Rec-C

D. Rec-D

A

Which of the following involves remarkable capacity of short segment of DNA to move from one place to another place in the genome?

A. DNA transposition

B. DNA replication

C. Translation

D. Transcription

A

In the process of homologous recombination, DNA molecules are regenerated by the process of genetic exchange. This is known as resolution. Which of the following events happen during resolution?

A. Cleavage and dissolution of the Holliday junction

B. Degeneration of duplex DNA molecule

C. Exchange of DNA fragments (strand invasion)

D. Heterochromatin structure formation

A

Direct repeats in the transposable element are present __________

A. Within the transposon

B. Either side of the inverted repeat

C. Only downstream the inverted repeat

D. Only upstream the inverted repeat

B

Which enzyme catalyzes the excision and insertion events conducted by transposons?

a) Transformase

b) Transposase

c) Ligase

d) Helicase

e) Polymerase

B

Which category of transposons accomplishes transposition through a process that involves the insertion of copies of an element that were synthesized from the element's RNA?

A. Cut and paste transposons

B. Replicative transposons

C. Retrotransposons

D. Cut and paste transposons and Replicative transposons

E. All of these

C

Which of the following is a transposable element found in the human genome?

A. LINES

B. SINES

C. Retrovirus-like elements

D. All of these

E. None of these

D

The............... enzyme is encoded by phage P1 and acts by binding to two sites in the recombining DNA.

A. Cre recombinase

B. DNA polymerase

C. Transcriptase

D. DNA recombinase

A

What is the name of the site where Cre enzyme acts?

a) COX

b) LOX

c) AOX

d) XOP

B

What is Cas9 and what is it responsible for?

A. an RNA molecule that binds to target DNA via complementary base pairing

B. a DNA sequence that binds the Cas9 protein

C. a viral protein that disrupts bacterial membranes

D. a protein enzyme that cuts both strands of DNA at sites specified by an RNA guide

D

In an experiment you use RNA polymerase without its sigma factor for transcription. What will be the result that you observe?

A. Increased expression

B. Specific transcription

C. Random transcription

D. No effect on transcription

C

In an experiment you mutate the C terminal domain of alpha subunit of the RNA polymerase. What will you expect to see?

a) Transcription is absent

b) Transcription is at random sites c) Transcription is less

d) Transcription is more

C