Ch. 12 Concept Check & Comprehension Questions

Question 1

Which of the following base sequences is used during transcription?

Answer 1

Promoter and terminator

Question 2

The three stages of transcription are..

Answer 2

Initiation, elongation, and termination

Question 3

Which of the following statements is false?

Answer 3

All genes encode polypeptides that function as units within proteins

Question 4

With regard to a promoter, a transcriptional state site is..

Answer 4

Located at the +1 position and is where the first base is used as a template for transcription

Question 5

For the following five sequences, what is the consensus sequence?
5'-GGGAGCG-3'
5'-GAGAGCG-3'
5'-GAGTGCG-3'
5'-GAGAACG-3'
5'-GAGAGCA-3'

Answer 5

5’-GAGAGCG-3’

Question 6

Sigma factor is needed during which stage of transcription?

Answer 6

Initiation

Question 7

A uracil-rich sequence occurs at the end of the RNA in..

Answer 7

p-independent termination

Question 8

Which RNA polymerase in eukaryotes is responsible for the transcription of genes that encode proteins?

Answer 8

RNA polymerase II

Question 9

An enhancer is a ___ that ___ the rate of transcription.

Answer 9

cis-acting element, increases

Question 10

The basal transcription apparatus is composed of..

Answer 10

• five general transcription factors
• RNA polymerase II
• a DNA sequence containing a TATA box and transcriptional start site

Question 11

With regard to transcriptional termination in eukaryotes, which model suggests that RNA polymerase is physically removed from the DNA?

Answer 11

Torpedo model

Question 12

Which of the following are examples of RNA modification?

Answer 12

• splicing
• 7-Methylguanosine cap
• PolyA tail

Question 13

A ribozyme is..

Answer 13

An RNA molecule with catalytic function

Question 14

Which of the following statements about the spliceosome is false?

Answer 14

A spliceosome removes exons from RNA molecules

Question 15

What are functions of the 7-methylguanosine cap?

Answer 15

• exit of mRNA from the nucleus
• efficient splicing of pre-mRNA
• initiation of translation

Question 16

What are key differences between bacteria and eukaryotes?

Answer 16

• initiation of transcription requires more proteins in eukaryotes
• a 7-methylguanosine cap is added only to eukaryotic mRNAs
• splicing is common in complex eukaryotes but not in bacteria

Question 17

Organization of sequences of a bacterial gene and it’s mRNA transcript.

If a mutation changed the start codon into a stop codon, would this mutation affect the length of the RNA? Explain.

Answer 17

The mutation would not affect the length of the RNA, because it would not terminate transcription. However, the encoded polypeptide would be shorter.

Question 18

What does the term consensus sequence mean?

Answer 18

When comparing a group of related sequences, the consensus sequence is the most common base found at each location within that sequence.

Question 19

The binding of sigma-factor protein to the promoter region.

Why is it necessary for portions of sigma-factor protein to fit into the major groove?

Answer 19

Parts of sigma-factor must fit into the major groove so it can recognize a base sequence of a promoter.

Question 20

The initiation stage of transcription in bacteria.

What feature of the –10 sequence makes it easy to unwind?

Answer 20

The –10 is AT rich, which has fewer hydrogen bonds compared to a region with a lot of GC base pairs.

Question 21

p-dependent termination.

What would be the consequences if a mutation removed the rut site from this RNA molecule?

Answer 21

The mutation would prevent p-dependent termination of transcription.

Question 22

p-independent or intrinsic termination.

Why is NusA important for this process?

Answer 22

NusA helps RNA polymerase to pause, which facilitates transcriptional termination.

Question 23

A common pattern for the promoter of protein-encoding genes recognized by RNA polymerase II.

What is the functional role of the TATA box?

Answer 23

The TATA box provides a precise starting point for the transcription of eukaryotic protein-encoding genes

Question 24

Steps leading to the formation of the open complex.

Why is carboxyl terminal domain (CTD) phosphorylation functionally important?

Answer 24

The phosphorylation of CTD allows RNA polymerase to proceed to the elongation phase of transcription

Question 25

The processing of a precursor tRNA molecule in E. coli.

What is the difference between an endonuclease and an exonuclease?

Answer 25

Ah endonuclease can cleave within a strand, whereas an exonuclease digests a strand, one nucleotide at a time, starting at one end.

Question 26

Mechanisms of RNA splicing.

Which of these three mechanisms is very common in eukaryotes?

Answer 26

Splicing via a spliceosome is very common in eukaryotes.

Question 27

Splicing of pre-mRNA via a spliceosome.

Describe the roles of snRNPs in the splicing process.

Answer 27

snRNPs are involved in recognizing the intron boundaries, cutting out the intron, and connecting the two adjacent exons together.

Question 28

Attachment of a 7-methylguanosine cap to the 5’ end of mRNA.

What are three functional roles of the 7-methylguanosine cap?

Answer 28

• proper splicing of pre-mRNA
• the exit of mRNA from the nucleus
• the binding of mRNA to a ribosome

Question 29

RNA editing by deamination.

What is a functional consequence of RNA editing?

Answer 29

That the amino acid sequence of an encoded polypeptide may be changed, which can affect its function