Question 1

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. This results in premature termination of polypeptide synthesis, leading to a truncated protein.

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 the promoter region of DNA, which signals the start site for transcription.

Question 3

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 4

What are micro RNAs?

Accepted Answer

Micro RNAs (miRNAs) are small regulatory RNAs that play crucial roles in regulating gene expression in a wide range of biological processes, including development, cell proliferation, differentiation, and apoptosis. They act by binding to the 3' untranslated region (UTR) of messenger RNAs (mRNAs) and promoting their degradation or inhibiting their translation into proteins.

Question 5

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 specific nucleotide sequences that allow for the binding of RNA polymerase and the initiation of transcription. The operator region is a regulatory sequence that controls the binding of RNA polymerase, while enhancer regions are regulatory sequences that can increase the transcriptional activity of a gene. The origin of replication is a sequence that is involved in the initiation of DNA replication, and the Shine-Dalgarno sequence is a nucleotide sequence found in bacterial mRNA that is involved in the initiation of translation.

Question 6

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

A missense mutation is a point mutation that results in a change in the amino acid specificity of the codon. This means that a different amino acid is inserted into the protein sequence as a result of the mutation. Frameshift mutations shift the reading frame of the codons, resulting in a completely different sequence downstream of the mutation. Silent mutations do not result in any change to the amino acid sequence. Nonsense mutations result in a premature stop codon, leading to a truncated protein. Amber is a stop codon, not a type of point mutation.

Question 7

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 can bind to RNA polymerase and direct it to specific promoters, thus controlling the expression of large sets of genes that are functionally related. This allows bacteria to rapidly adapt to changes in their environment and perform different biological functions as needed.

Question 8

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

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end of a growing DNA strand, therefore new nucleotides are always added in the 5' to 3' direction.

Question 9

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

Accepted Answer

Deletion of base pairs results in a frameshift mutation, where the reading frame is shifted and the amino acid sequence is disrupted from that point onwards. This can lead to altered or truncated proteins.

Question 10

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

Accepted Answer

This is because Archaea and Eukarya both have similar replication machinery, including the use of histones for DNA packaging and the presence of multiple origins of replication. Bacteria, on the other hand, have a simpler replication process with a single origin of replication and no histones.

Question 11

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 12

Replication of eukaryal DNA requires RNA primer synthesis.

Accepted Answer

Eukaryal DNA replication requires RNA primers to initiate DNA synthesis by DNA polymerase. The RNA primers are later replaced by DNA nucleotides.

Question 13

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

Accepted Answer

Most bacterial promoters consist of two regions: Pribnow box (also known as the -10 region) and -35 region.

Question 14

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 15

Which of these would a signal peptide be used for?

Accepted Answer

A signal peptide is used to move a protein to the outside of the cell. It is a short amino acid sequence present at the N-terminus of newly synthesized proteins that directs the protein to the secretory pathway for secretion outside the cell or for insertion into the cell membrane.

Question 16

In eukaryal cells,what does RNA polymerase II transcribe?

Accepted Answer

RNA polymerase II transcribes mRNA genes in eukaryal cells.

Question 17

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 ribosomal binding site is located nearer the 5' end of the mRNA molecule and is called the Shine-Dalgarno sequence. Therefore, choice D (5'; Shine-Dalgarno sequence) is the correct answer. Choices A, B, C, and E are incorrect since they either have the wrong end of the mRNA molecule or refer to different sequences altogether.

Question 18

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 aid in protein folding by providing a stable environment for the polypeptide to fold into its appropriate conformation. Proteases, cytokines, peptidases, and lipases are not involved in protein folding.

Question 19

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

Eukaryotic RNA undergoes additional processing, including 5' capping with a 7-methyl-guanosine and 3' polyadenylation. Additionally, large internal sequences called introns are removed by spliceosomes to produce a functional mRNA that consists only of coding sequences called exons. Therefore, the correct description of eukaryotic RNA processing is capping the 5' end with 7-methyl-guanosine, adding a poly-A sequence at the 3' end and removing internal sequences called introns. Choice A is incorrect because it says that introns are removed from the 3' end when they are actually removed from the middle of the RNA molecule. Choice B is incorrect because it says that exons are removed when they are actually kept in the final mRNA. Choice D is incorrect because it says that exons are removed from the mRNA when they are actually kept in the final mRNA. Choice E is incorrect because it only includes some of the steps of eukaryotic RNA processing but does not include intron removal.

Question 20

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

Accepted Answer

Polycistronic mRNA contains the code for multiple peptides. This means that multiple genes are transcribed into a single mRNA molecule, and therefore multiple proteins can be translated from a single mRNA molecule.

Quiz 7: DNA Replication and Gene Expression