Exam 2 material

Question 1

Antiviral drugs that act at the level of host recognition are designed to:

A. Prevent endocytic vesicle formation

B. Prevent virus binding to the host cell receptor

C. Enhance antibody production

D. Inactivate viral nucleic acid polymerases

E. Bind to viral metabolic enzymes

Answer 1

B. Prevent virus binding to the host cell receptor

Question 2

Small non-coding RNA molecules (sRNA) affect gene expression at the level of:

A. DNA synthesis

B. Transciption initiation

C. Post-transcriptional processing

D. Translation

E. Post-translational modifications

Answer 2

D. Translation

Question 3

Initiation of translation in bacteria starts with the binding of the 30S ribosomal subunit to the mRNA molecule. The ribosomal binding site is nearer the ______ end of the mRNA molecule and is called the ______.

A. 3’; Pribnow box

B. 3’; Shine-Dalgarno sequence

C. 3’; Rho sequence

D. 5’; Shine-Dalgarno sequence

E. 5’; Rho sequence

Answer 3

D. 5’; Shine-Dalgarno sequence

Question 4

Once the auto-inducer excreted by Vibrio fischeri reaches a critical condition, it is able to diffuse back into the cell. What is its next action?

A. Bind to the bacterial luciferase to produce luminescence

B. Inactivate a tanscriptional repressor to allow transcription of lux genes

C. Bind to a transcriptional activator to increase transcription rates of the lux genes

D. Be cleaved by a protease to produce luminescence

E. Bind to the promoter to enhance transcription of the lux genes

Answer 4

C. Bind to a transcriptional activator to increase transcription rates of the lux genes

Question 5

Which of these is a point mutation that results in changing a codon from an amino acid codon to a stop codon?

A. Frameshift

B. Silent

C. Nonsense

D. Missense

E. Deletion

Answer 5

C. Nonsense

Question 6

Viruses that load their nucleic acid into pre-assembled capsids use what type of assembly mechanism?

A. Concerted

B. Tetrahedral

C. Sequential

D. Irregular

E. Helical

Answer 6

C. Sequential

Question 7

Genes that are constitutively expressed are:

A. Regulated by repression

B. Unregulated

C. Regulated by induction

D. Regulated by activation

E. Regulated by attenuation

Answer 7

B. Unregulated

Question 8

An HIV mutant has been identified that is resistant to the drug AZT. What viral gene is the most likely to contain a mutation?

A. Reverse transcriptase

B. Viral attachment protein

C. DNA integrase

D. gp41 membrane fusion protein

E. Viral mRNA polymerase

Answer 8

A. Reverse transcriptase

Question 9

Isopropyl β-d-1-thiogalactopyranoside (IPTG), a lactose analog, acts as an inducer of lac operon. What is its mode of action?

A. It functions as a co-activator of gene expression

B. It inactivates the Lacl repressor protein

C. It activates the enzyme β-galatosidase

D. It binds the RNAP for enhanced binding to the promoter

E. It binds to the operator to enhance transcription initiation

Answer 9

B. It inactivates the Lacl repressor protein

Question 10

The mRNA of bacterial cells is polycistronic. What does this term mean?

A. It can be translated more than once

B. It contains the code for multiple peptides

C. It can be translated from either end

D. It is transcribed from multiple sites on the chromosome

E. The translated protein may be modified in different ways

Answer 10

B. It contains the code for multiple peptides

Question 11

What is a codon?

A. Four bases on the mRNA that is read by the ribosome in the 3’ to 5’ direction

B. Four bases on the mRNA that is read by the ribosome in the 5’ to 3’ direction

C. Three bases on the mRNA that is read by the ribosome in the 3’ to 5’ direction

D. Three bases on the mRNA that is read by the ribosome in the 5’ to 3’ direction

E. Two bases on the mRNA that is read by the ribosome in the 5’ to 3’ direction

Answer 11

D. Three bases on the mRNA that is read by the ribosome in the 5’ to 3’ direction

Question 12

What is the term for cells that can naturally take up extracellular DNA?

A. Porous

B. Competent

C. Conjugant

D. Susceptible

E. Primed

Answer 12

B. Competent

Question 13

Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) separates proteins based on:

A. Size

B. Charge

C. Hydrophobicity

D. Size and charge

E. Size and hydrophobicity

Answer 13

D. Size and charge

Question 14

What is the correct sequence of protein action during DNA replication?

1. DNA polymerase
2. Single stranded binding proteins
3. DNA ligase
4. Helicase
5. Primase

A. 5-4-1-2-3

B. 4-5-2-1-3

C. 2-5-4-1-3

D. 5-1-2-4-3

E. 4-5-1-3-2

Answer 14

B. 4-5-2-1-3

Question 15

The Hershey and Chase experiment was able to conclusively demostrate that DNA, not protein, was the genetic material. They were able to distinguish DNA from protein since labeled ____ incorporated into DNA while labeled ____ incorporated into proteins.

A. Nitrogen; sulfur

B. Magnesium; nitrogen

C. Nitrogen; magnesium

D. Phosphorus; sulfur

E. Sulfur; nitrogen

Answer 15

D. Phosphorus; sulfur

Question 16

Nucleoside analogs, such as AZT, are drugs that are structurally similar to normal nucleosides, but contain a chemical side group that poisons the viral particle.

A. True

B. False

Answer 16

B. False

Question 17

All DNA viruses replicate in the nucleus, using host cell polymerases and all RNA viruses replicate in the cytoplasm of the host cell, using virally-encoded polymerases.

A. True

B. False

Answer 17

B. False

Question 18

Two component regulatory response systems are not signal-specific.

A. True

B. False

Answer 18

B. False

Question 19

Despite the apparent waste of energy, one mechanism to regulate mRNA expression is to enzymatically degrade mRNA molecules following transcription.

A. True

B. False

Answer 19

A. True

Question 20

All living oragnisms use the same genetic code for the translation of mRNA.

A. True

B. False

Answer 20

A. True

Question 21

A Northern blot uses a probe to hybridize to RNA fragments that have been separated by electrophoresis.

A. True

B. False

Answer 21

A. True

Question 22

A genomic library consists of a collection of cloned fragments that comprise the genomes of a large number of organisms.

A. True

B. False

Answer 22

B. False

Question 23

The enzyme telomerase is found in both bacterial and eukaryotic cells.

A. True

B. False

Answer 23

B. False

Question 24

Short answer: Why are multiple organisms of replication necessary for DNA replication in eukaryotes?

Answer 24

There is much more DNA to replicate in eukaryotes

Question 25

**Short answer:** Describe the process of mRNA processing in eukaryotic cells

Answer 25

* 5' cap added * Poly(A) tail added * Introns spliced out

Question 26

**Short answer:** How are the enzymes reverse transcriptase and integrase involved in retrovirus replication in host cells?

Answer 26

* the virus uses its own _reverse transcriptase_ to make dsDNA from its RNA. * Then the new DNA is then incorporated into the host cell genome by an _integrase._

Question 27

**Short answer:** Why is the genetic code considered degenerate?

Answer 27

because more than one codon sequence can code for the same amino acid

Question 28

**Short answer:** Explain the mechanism of attenuation and its role in regulation of gene expression.

Answer 28

the interaction between translation and transcription processes. terminates or stalls transcription Role: controls transcription by mRNA secondary structure, control biosynthetic pathways (Trp operon)

Question 29

**Short answer:** Explain why viruses of mammals generally undergo some form of uncoating, but viruses of bacteria usually do not.

Answer 29

Most viruses of animals enter the host cell cytoplasm as an intact particle surrounded by a protein shell, so the viral genome must be released from the shell in order to replicate. Viruses of bacteria just inject their genomes directly into the host cell cytoplasm without a shell surrounding it so no uncoating is needed.

Question 30

**Short answer:** What is transduction? Explain the role of bacteriophage in the process.

Answer 30

The virus accidently packages host material and transfers to another cell. Bacteriophage is the vector used to transfer the material from one cell to another cell.

Question 31

**Short answer:** Describe the difference between transcription initiation in Bacteria and Eukarya.

Answer 31

_Bacteria_ * _​_α factor and polymerase go to promoter @ the same time _Eukarya_ * Transcription factors bind individually and then polymerase comes in after

Question 32

**Short answer:** What role does tryptophan play in *trp* operon regulation?

Answer 32

Tryptophan is the amino acid that is constantly being released in the system. When tryptophan becomes excessive in the system, a **_co-repressor activates_** and this activation halts transcription and the production of tryptophan.