Question 1

There are 2 consensus sequence elements within the promoter sequence.Which of the following are they?

Accepted Answer

The correct consensus sequence elements within the promoter sequence are the Pribnow box near -10 with a sequence of TATAAT and the -35 region containing the consensus TTGACA. These elements are crucial for the binding of RNA polymerase and the initiation of transcription in prokaryotes.

Question 2

Which of the following subunits in E.coli RNA polymerase is required for recognition of the promoter sequence?

Accepted Answer

The σ (sigma) subunit is responsible for recognizing the promoter sequence in E.coli RNA polymerase.

Question 3

The non-template strand has the same nucleotide sequence and direction as that of the RNA transcript.Which of the following parts of the mRNA encodes the N-terminus of the protein?

Accepted Answer

The N-terminus of a protein corresponds to the amino acid at the beginning of the peptide chain. Translation of the mRNA always starts at the 5'-end, and the first codon encodes the N-terminal amino acid of the protein. Therefore, the 5'-end of the mRNA encodes the N-terminus of the protein.

Question 4

Which of the following is NOT a stage in transcription?

Accepted Answer

DNase I activity is not a stage in transcription. The other stages include binding of RNA polymerase holoenzyme at the promoter sites, initiation of polymerization, and chain elongation.

Question 5

Operons are regulatory sequences lying adjacent to the DNA being transcribed and are composed of a promoter located next to an operator.Which of the following interacts with and controls the operator?

Accepted Answer

The answer of Operons are regulatory sequences lying adjacent to...

Question 6

Which of the following is NOT a factor or subunit contained within the E.coli RNA polymerase holoenzyme in prokaryotic organisms?

Accepted Answer

ρ(rho) is not a factor or subunit contained within the E.coli RNA polymerase holoenzyme in prokaryotic organisms. The other choices (α, β, and β prime) are all subunits of the E.coli RNA polymerase holoenzyme.

Question 7

In order for transcription to begin,the DNA-duplex must be "opened" to allow RNA polymerase access to single-stranded template.Which of the following facilitates "opening" of DNA-duplex?

Accepted Answer

Binding of RNA polymerase s-subunit facilitates the opening of the DNA duplex, allowing access to the single-stranded template. The s-subunit recognizes the promoter region and initiates the transcription process. A high melting temperature (Tm) in the Pribnow box or a G:C-rich DNA duplex may affect the stability of the DNA duplex but does not directly facilitate its opening. Positive supercoiling can also facilitate the formation of the open complex for transcription, but it is not the only factor involved in the process.

Question 8

Which of the following terms is for the specific sequences in DNA that determine intrinsic RNA chain cessation?

Accepted Answer

Termination refers to the specific sequences in DNA that determine intrinsic RNA chain cessation. The other options, rho binding, template binding, and supercoil, are not directly related to this process.

Question 9

Which of the following does single polycistronic mRNA encode for in bacteria?

Accepted Answer

In bacteria, a single polycistronic mRNA encodes for multiple enzymes of a particular metabolic pathway. This is achieved through the presence of multiple coding sequences (cistrons) within a single mRNA molecule. Each cistron codes for a separate protein product and they are often related to one another in function. The polycistronic mRNA is translated in a consecutive manner by ribosomes, producing a series of separate proteins encoded by the different cistrons.

Question 10

Which of the following factors is an ATP-dependent helicase utilized in one of the termination mechanisms in bacteria?

Accepted Answer

The ATP-dependent helicase utilized in one of the termination mechanisms in bacteria is ρ (rho) factor. It binds to the nascent mRNA and moves along it, unwinding the RNA duplexes with the help of ATP hydrolysis. When ρ factor encounters a pause site created by a GC-rich sequence at the 3' end of the RNA, it destabilizes the RNA polymerase complex, leading to termination of transcription.

Question 11

Which of the following terms defines nucleotide sequences that identify the location of transcription start sites and regulate the level of transcription?

Accepted Answer

Promoters are nucleotide sequences that identify the location of transcription start sites and regulate the level of transcription. Sigma factors are proteins that bind to promoters to initiate transcription, Pribnow box is a specific sequence within bacterial promoters, and TATA box is a specific sequence within eukaryotic promoters. However, promoters are not restricted to a particular group of organisms and are generally defined as the regions of DNA that interact with transcription factors to initiate transcription.

Question 12

Which of the following base locations in DNA specifies the first base in the RNA transcript designated,and what numerical value is it assigned?

Accepted Answer

The transcription start site is the location in DNA where transcription actually begins, and it is assigned a numerical value of +1. Therefore, base D, "transcription start site;+1," is the correct answer. The promoter is a sequence of DNA that signals the start of transcription and is typically located upstream of the transcription start site. The enhancer is another type of regulatory sequence that can activate or enhance transcription, but it is not typically used to designate specific base locations.

Question 13

Which of the following is a characteristic of rho (ρ)factor?

Accepted Answer

Rho factor is a helicase that terminates transcription by binding to RNA at specific sites that are free of ribosomes, allowing it to catch up to the RNA polymerase and release the nascent RNA.

Question 14

Which of the following is where are nucleotides said to lie relative to the transcription site when they are in the "minus" direction?

Accepted Answer

In molecular biology, the terms "plus" and "minus" are used to indicate the direction of a DNA strand relative to the direction of transcription. In the "plus" direction, nucleotides are said to lie upstream of the transcription site, while in the "minus" direction, nucleotides are said to lie downstream of the transcription site. Therefore, the best answer is B, upstream.

Question 15

Which of the following is NOT a characteristic of the prokaryotic promoter for the rrn gene in E.coli?

Accepted Answer

The prokaryotic promoter for the rrn gene in E.coli typically includes both a -10 region (Pribnow box) and a -35 region consensus sequence. The statement that it lacks a -35 region consensus sequence is incorrect.

Question 16

Treatment of the RNA polymerase/DNA complex with DNase in vitro is a DNA footprinting technique.Which of the following is the technique used for?

Accepted Answer

DNA footprinting is used to locate the promoter site in this context. By treating the RNA polymerase/DNA complex with DNase, the enzyme will only cut the unprotected regions of DNA which are not bound to the RNA polymerase. This leaves a "footprint" of the DNA protected by the polymerase, which can be visualized by gel electrophoresis. By comparing the DNase-treated DNA to untreated DNA, the location of the RNA polymerase can be determined and therefore the location of the promoter site can be inferred.

Question 17

Which of the following is thought to be generated by transcription chain elongation?

Accepted Answer

As the RNA polymerase moves along the DNA template strand during transcription, it generates positive supercoils ahead of the transcription bubble due to the unwinding of the DNA double helix. These positive supercoils can cause stress and potentially hinder the transcription process if not resolved appropriately.

Question 18

The stand of dsDNA that is read by RNA polymerase is termed the template strand with RNA polymerase moving 3'?5' along it.Which of the following does the polymerase form,and in which direction does it grow?

Accepted Answer

RNA polymerase forms a transcript (RNA molecule) and grows 5'→3' along the template strand.

Question 19

Which of the following processes is used by both prokaryotes and differentiated eukaryotic cells when they express a small number of their genes at any given time?

Accepted Answer

Both prokaryotes and differentiated eukaryotic cells regulate the expression of their genes by only transcribing a small number of them at any given time. This allows the cell to conserve energy and resources by producing only the proteins needed for specific cellular functions. Translation, replication, and repair are not necessarily linked to gene expression regulation in the same way that transcription is.

Question 20

The initiation site binds a purine nucleotide base pairing with the +1 base exposed within the open promoter complex.Which of the following is where the second base is added?

Accepted Answer

The second base is added to the 3'-O (3'-hydroxyl group) of the first base during RNA synthesis, as nucleotides are added to the 3' end of the growing RNA chain.

Quiz 29: Transcription and the Regulation of Gene Expression