Question 1

The genes encoding the chloroplast RNA polymerase are not similar in sequence to those of RNA polymerase in cyanobacteria.

Accepted Answer

The genes encoding the chloroplast RNA polymerase are similar in sequence to those of RNA polymerase in cyanobacteria, reflecting the evolutionary origin of chloroplasts from an ancestral cyanobacterial endosymbiont.

Question 2

TFIIB can bind to DNA in the absence of TFIID.

Accepted Answer

TFIIB binding to DNA generally requires the prior binding of TFIID to the TATA box, as TFIID's binding helps to recruit TFIIB and other transcription factors to form the pre-initiation complex.

Question 3

The genes present vary among cell types,for example,pancreatic cells carry the gene for insulin,but skin cells do not.

Accepted Answer

All cells in an organism (except for sperm and egg cells and red blood cells) contain the same set of genes, but different genes are activated or expressed in different cell types. Pancreatic cells express the insulin gene, while skin cells do not, but both cell types contain the gene.

Question 4

Consensus sequences are found in TATA box and - 35 regions of promoters that are strong but not in those that are weak.

Accepted Answer

Consensus sequences, including those in the TATA box and -35 regions, can be found in both strong and weak promoters. The strength of a promoter often depends on how closely its consensus sequences match the ideal or most common sequence, not on the presence or absence of these sequences.

Question 5

Pause sites contain more GC base pairs than AT base pairs.

Accepted Answer

Pause sites, which are regions in DNA or RNA where the RNA polymerase temporarily stops or slows down during transcription, do not necessarily contain more GC base pairs than AT base pairs. The presence of GC or AT base pairs in pause sites can vary and is not a defining characteristic of these regions.

Question 6

Rho-dependent termination requires exposure of single-stranded RNA.

Accepted Answer

Rho-dependent termination relies on the binding of Rho factor to the exposed single-stranded RNA region created by RNA polymerase during transcription. Rho factor then travels along the RNA molecule and disrupts the RNA polymerase, leading to termination of transcription.

Question 7

Eukaryotic RNA polymerases do not bind on their own to DNA templates but prokaryotic RNA polymerases do.

Accepted Answer

Eukaryotic RNA polymerases require the assistance of various transcription factors to bind to DNA templates, whereas prokaryotic RNA polymerases can bind directly to DNA templates without the need for additional factors.

Question 8

Class I genes encode large ribosomal RNA.

Accepted Answer

Class I genes encode large ribosomal RNA, while Class II genes encode small ribosomal RNA and Class III genes encode transfer RNA.

Question 9

Rho-dependent termination occurs at pause sites within the coding region.

Accepted Answer

Rho-dependent termination typically occurs at specific sites in the DNA called terminator sequences, which are located at the end of the gene or operon, not within the coding region.

Question 10

RNA polymerase requires a high-precision fit when catalyzing the formation of a new phosphodiester linkage.

Accepted Answer

RNA polymerase uses precise base-pairing interactions to ensure the correct positioning of incoming nucleotides for the formation of a new phosphodiester linkage. Any error in positioning can result in errors in the resulting RNA sequence.

Question 11

Transcription is the process by which the information in mRNA molecules is interpreted and the appropriate proteins synthesized.

Accepted Answer

Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA); translation is the process by which the information in mRNA molecules is interpreted and the appropriate proteins synthesized.

Question 12

RNA polymerase has a higher error rate (one mutation for every 1 million nucleotides incorporated)than DNA polymerase because RNA polymerase does not have exonuclease proofreading activity but DNA polymerase does.

Accepted Answer

RNA polymerase does not have exonuclease proofreading activity, whereas DNA polymerase has proofreading activity that enables it to correct errors during DNA replication. Because RNA polymerase does not have this proofreading ability, it has a higher error rate compared to DNA polymerase.

Question 13

RNA polymerase catalyzes DNA-directed RNA synthesis.

Accepted Answer

RNA polymerase is responsible for catalyzing the synthesis of RNA strands using the DNA template as a guide.

Question 14

A transcription complex does not form when one or more proteins bind to the promoter sequence and to RNA polymerase in eukaryotes.

Accepted Answer

A transcription complex does form when one or more proteins bind to the promoter sequence and to RNA polymerase in eukaryotes.

Question 15

The same RNA polymerase that transcribes the ribosomal RNA transcribes all mitochondrial genes.

Accepted Answer

Mitochondria have their own DNA and RNA polymerase, which transcribe mitochondrial genes. The ribosomal RNA is a type of RNA typically produced by the nucleolus in the nucleus of the cell, and is not directly related to mitochondrial gene expression.

Question 16

The large RNA-protein complex that processes introns and exons is called ________.
A)the replisome
B)the catalytic RNA complex
C)the spliceosome
D)RNA ligase

Accepted Answer

The large RNA-protein complex that processes introns and exons is called the spliceosome. The other options are not involved in RNA splicing. A is involved in DNA replication, B refers to RNAs that catalyze chemical reactions, and D is involved in joining separate RNA strands or RNA to DNA.

Question 17

In E.coli,all transcription termination requires a specific protein,rho.

Accepted Answer

While rho-dependent termination is one mechanism of transcription termination in E. coli that requires the protein rho, there are also rho-independent mechanisms that do not require this protein. Therefore, not all transcription termination in E. coli requires rho.

Question 18

Operons exist in bacteria but not in eukaryotic cells since several genes are often transcribed from a single bacterial promoter.

Accepted Answer

Operons are a feature of bacterial cells, and refer to a cluster of related genes that are controlled by a single promoter region. In contrast, eukaryotic cells typically have individual promoters for each gene, and do not have operons.

Question 19

A small percentage of the total RNA in a cell is ribosomal RNA.

Accepted Answer

The majority of RNA in a cell is ribosomal RNA (rRNA), making up about 80% of the RNA in the cell, which is involved in protein synthesis.

Question 20

The unwinding of DNA at the initiation site is an example of a conformational change.

Accepted Answer

The unwinding of DNA at the initiation site involves breaking the hydrogen bonds between the base pairs, resulting in a conformational change in the DNA structure.

Quiz 21: Transcription and RNA Processing