Question 1

What does Rho-independent termination of transcription in bacteria involve?

Accepted Answer

Rho-independent termination involves the formation of a hairpin loop in the RNA molecule, which is followed by a sequence of uracil (poly U) bases. This structure causes the RNA polymerase to pause and then dissociate from the DNA template, ending transcription.

Question 2

What is the sigma factor of the RNA polymerase holoenzyme responsible for?

Accepted Answer

The sigma factor of the RNA polymerase holoenzyme is responsible for recognizing and binding to the promoter region on the DNA, thereby initiating transcription. Once the polymerase is bound to the promoter, the sigma factor will dissociate, allowing for transcription elongation to occur.

Question 3

After the translational process the polypeptide folds into the appropriate conformation for proper functioning.What group of proteins aids in protein folding?

Accepted Answer

Chaperonins are a group of proteins that assist in the proper folding of polypeptides by providing a protective environment for the folding process to occur. Proteases, cytokines, peptidases, and lipases are not involved in protein folding.

Question 4

Replication of eukaryal DNA requires RNA primer synthesis.

Accepted Answer

Eukaryal DNA replication requires RNA primer synthesis before DNA polymerase can begin synthesizing new DNA strands. The RNA primer provides a short, single-stranded template for DNA polymerase to extend from.

Question 5

The RNA polymerase in Archaea is more similar to Bacteria RNA polymerase than Eukarya RNA polymerase II.

Accepted Answer

The RNA polymerase in Archaea is more similar to Eukarya RNA polymerase II than to Bacteria RNA polymerase, reflecting a closer evolutionary relationship between Archaea and Eukaryotes in terms of their transcription machinery.

Question 6

The DNA replication process in Archaea more closely resembles that in Eukarya than in Bacteria.

Accepted Answer

Archaea and Eukarya share many similarities in terms of their DNA replication process, including the presence of histones and the use of a replisome complex. Bacteria, on the other hand, have a simpler DNA replication process that lacks histones and uses a different set of proteins for replication.

Question 7

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

Accepted Answer

A nonsense mutation is a point mutation where a codon that codes for an amino acid is changed to a stop codon, resulting in premature termination of protein synthesis. Frameshift mutations involve the insertion or deletion of one or more nucleotides, which changes the reading frame of the mRNA sequence, affecting all subsequent codons. Silent mutations do not change the amino acid sequence of the protein, and missense mutations result in a codon that codes for a different amino acid than the original codon. Deletions involve the removal of one or more nucleotides, which can lead to a frameshift mutation or a change in the codon sequence.

Question 8

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 ________.

Accepted Answer

The Shine-Dalgarno sequence is a short sequence of nucleotides located at the 5' end of the bacterial mRNA molecule that serves as the ribosomal binding site. The 30S ribosomal subunit binds to the Shine-Dalgarno sequence to initiate translation. The Pribnow box is a sequence of nucleotides located upstream of the start codon in bacterial genes and is involved in transcription initiation. The Rho sequence is a sequence of nucleotides in bacterial genes that serves as a termination signal for transcription.

Question 9

For the initiation of transcription in bacteria,RNA polymerase binds to what region on the gene?

Accepted Answer

RNA polymerase binds to the promoter region on the gene to initiate transcription in bacteria. The promoter region contains the specific DNA sequence recognized by RNA polymerase and is typically located upstream of the gene being transcribed.

Question 10

What are micro RNAs?

Accepted Answer

Micro RNAs (miRNAs) are small, non-coding regulatory RNAs that are typically 21-25 nucleotides in length. They play a crucial role in gene expression by binding to mRNA sequences and regulating their translation into proteins. MiRNAs are involved in many biological processes, including development, differentiation, cell cycle regulation, and apoptosis.

Question 11

Which of these is a term for a point mutation that results in a change in the amino acid specificity of the codon?

Accepted Answer

Missense mutations are point mutations that result in a change in the amino acid specificity of the codon. Frameshift mutations result in the insertion or deletion of nucleotides, which causes a shift in the reading frame and alters the entire amino acid sequence. Silent mutations do not affect the amino acid sequence because they do not result in a change in the codon. Nonsense mutations create a premature stop codon, which prematurely terminates translation. Amber is a type of stop codon.

Question 12

Which of these results from a deletion of base pairs such that the amino acid sequence is disrupted from that point downward?

Accepted Answer

A deletion of base pairs causes a frameshift mutation where the reading frame is shifted, and the amino acid sequence is disrupted from that point downwards. Frameshift mutations usually result in alterations to the amino acid sequence and a non-functional or truncated protein.

Question 13

In the same bacterial cell,different sigma factors are able to control the expression of large blocks of genes.

Accepted Answer

Different sigma factors in bacteria are responsible for recognizing specific promoter sequences and initiating the transcription of genes. Each sigma factor controls the expression of a different set of genes or operons, allowing bacteria to rapidly adapt to changes in their environment or growth conditions. Therefore, it is true that different sigma factors can regulate large blocks of genes in the same bacterial cell.

Question 14

Which of these would a signal peptide be used for?

Accepted Answer

Signal peptides are used to move proteins from inside the cell to the outside of the cell. They function like addresses that guide the protein to the appropriate organelle or location within or outside the cell.

Question 15

Transcription termination in eukaryal cells is more complex than in bacterial cells as the RNA molecule undergoes further processing before becoming a functional mRNA.Which of these BEST describes this processing?

Accepted Answer

Eukaryal cells process the pre-mRNA molecule by capping the 5' end with 7-methyl-guanosine, adding a poly-A sequence at the 3' end, and removing internal sequences called introns. This process is called RNA splicing, and it results in the mature mRNA molecule. This process is more complex than in bacterial cells, which only need to add a termination signal to the mRNA molecule. Option A, B and D are incorrect because they suggest that exons are removed, which is not true. Option E is incorrect because it suggests capping the 3' end, whereas capping occurs at the 5' end.

Question 16

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

Accepted Answer

Polycistronic mRNA refers to a type of mRNA transcript that contains the coding sequence for multiple genes or peptides. Therefore, option B is the correct answer.

Question 17

What is a codon?

Accepted Answer

A codon consists of three nucleotide bases on mRNA and is read by the ribosome in the 5' to 3' direction.

Question 18

In DNA replication nucleotides are always added in the 5' to 3' direction.

Accepted Answer

DNA polymerase can only add nucleotides in the 5' to 3' direction due to the chemical structure of the DNA molecule. This means that the leading strand of DNA is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously in the opposite direction, resulting in Okazaki fragments that are later joined together by DNA ligase.

Question 19

In eukaryal cells,what does RNA polymerase II transcribe?

Accepted Answer

RNA polymerase II transcribes mRNA genes in eukaryal cells.

Question 20

Most bacterial promoters consist of two regions: __________ and ___________.

Accepted Answer

The Pribnow box (TATAAT) is located around -10 region while -35 region (TTGACA) is located around -35 upstream from the transcription start site. Therefore, the bacterial promoter consists of two regions: Pribnow box and -35 region.

Quiz 7: DNA Replication and Gene Expression