Question

1 Which of the following is not a mechanism by which plasmids ensure their inheritance and maintenance during cell division?

Choose one:

A.   carrying self-preservation genes, known as addiction modules

B.   high-copy-number plasmids

C.   carrying antibiotic resistance genes

D.   carrying partitioning system genes, parC, parM, and parR

E.   low-copy-number plasmids

2 While plasmid replication is not tied to chromosomal replication, many of the proteins used for plasmid replication are host enzymes. Each plasmid contains its own origin of replication (ori) and only the few genes needed for replication. Which of the following proteins is needed for the rolling-circle mechanism of plasmid replication and is encoded by a plasmid gene?

Choose one:

A.   DNA polymerase III (Pol III)

B.   DNA ligase

C.   RepA

D.   ParC

E.   single-stranded DNA-binding protein

3Which of the following statements is true about the rolling-circle mechanisms of plasmid replication?

Choose one:

A.   RepA nicks the single-stranded RNA plasmid.

B.   RepA nicks both strands of the double-stranded DNA plasmid.

C.   RepA nicks the single-stranded DNA plasmid.

D.   RepA nicks one strand of the double-stranded DNA plasmid.

4 Analysis of the genome of a newly discovered bacterial strain reveals that it is composed of a double-stranded DNA molecule containing 16% thymine. Based on this information, what would you predict the percentage of cytosine to be?Choose one:

A.   34%

B.   16%

C.   68%

D.   32%

5 Both DNA sequencing and polymerase chain reactions (PCR) require __________ in order to synthesize a new DNA molecule.Choose one:

A.   primers

B.   dideoxynucleotides (ddNTPs)

C.   fluorescent nucleotides

D.   restriction endonucleases

E.   reverse transcriptase

6 In nature, RNA molecules tend to form “hairpin” structures, which have a variety of biological functions. These hairpin structures areChoose one:

A.   RNA-protein structures that form when regulatory proteins bind to the RNA molecule.

B.   RNA-RNA double-stranded regions that form when complementary nucleotides within the primary RNA sequence hydrogen bond.

C.   RNA-DNA structures that form when complementary RNA sequences hybridize with single-stranded DNA molecules.

D.   RNA-plasmid DNA structures that form when plasmids are replicated.

7 Identify which of the following statements are true about an operon.Choose one or more:

A. Multiple protein products can be produced by a single operon.

B. Multiple RNA molecules are produced by a single operon.

C. Operons produce monocistronic messages.

D. All genes in an operon are controlled by a single promoter.

8 A DNA chain can only grow if a ____________group is available on the growing DNA strand. Dideoxynucleotides are essential to the Sanger sequence reaction because ddNTPs have a __________

at this critical position and therefore cannot form a phosphodiester bond with an incoming nucleotide.

9 Which of the following is not a required component of the Sanger sequencing reaction mixture?Choose one:

A.   DNA polymerase

B.   primers

C.   dideoxynucleotides

D.   DNA helicase

E.   template DNA

F.   deoxynucleotides

Answer 1

1. Low-copy-number plasmids risk loss during cell division.

Answer is E) low-copy-number plasmids

2. In case of the rolling-circle mechanism of plasmid replication, the repA is required for replication. RepA binds to the ori site of the plasmid and is encoded by a plasmid gene.

Answer is C) RepA

3. In rolling circle mechanism, RepA binds to the ori site of the plasmid and nicks one strand of the double-stranded DNA plasmid.

Answer is D) RepA nicks one strand of the double-stranded DNA plasmid

4. As thymine is 16%, so adenine will also be 16% because A=T. Therefore, A+T = 32%.

We know, A+T+G+C = 100%

So, G+C = (100-32)%

That is 68%

Therefore, cytosine is (68/2)%, that is 34%.

Answer is A) 34%

5. Both DNA sequencing and PCR require primers to synthesize new DNA molecules. The reaction mixture for both DNA sequencing and PCR are incomplete without primers and the reaction will not start in the absence of primers.

Answer is A) Primers

6. The hairpin structures formed by the RNA molecules are a result of RNA-RNA double-stranded regions that form when complementary nucleotides within the primary RNA sequence hydrogen bond. The RNA strand folds and forms base pairs with another section of the same strand. The resulting structure looks like a loop or a U-shape.

Answer is B) RNA-RNA double-stranded regions that form when complementary nucleotides within the primary RNA sequence hydrogen bond.

7. All the genes in an operon are controlled by a single promoter. The number of promoter and operator is not affected by the number of genes present in the operon.

Answer is D) All genes in an operon are controlled by a single promoter.

8. A DNA chain can only grow if a 3' OH group is available on the growing DNA strand. Dideoxynucleotides are essential to the Sanger sequence reaction because ddNTPs lacks a 3' OH group which is required to terminate the chain on the attachment of the dideoxynucleotides.

9. The Sanger sequencing reaction mixture essentially contains DNA polymerase, primers, dideoxynucleotides, deoxynucleotides and a template DNA. DNA helicase has no role in Sanger sequencing.

Answer is D) DNA helicase