Question 1

Which statement about RNA polymerase is false?
A)The large beta subunit comprises the active site of the enzyme.
B)The alpha subunits are the scaffold for assembly of the other subunits.
C)The role of the omega subunit is well characterized.
D)All of the above are false.

Accepted Answer

The role of the omega subunit is not well characterized and is still unclear.

Question 2

Which subunit of the E.coli core RNA polymerase (a2bb'w)contributes to DNA binding?
A)a
B)b
C)b'
D)w

Accepted Answer

The b' subunit of the E.coli core RNA polymerase is known to be important for DNA binding. It contains a DNA-binding domain that interacts directly with the promoter region of the DNA. The other subunits (a, b, and w) are not directly involved in DNA binding.

Question 3

Weak promoters contain
A)no consensus sequences.
B)sequences that match consensus sequences poorly.
C)no TATA box or -35 regions.
D)TAT boxes but no -35 regions.

Accepted Answer

Weak promoters typically have sequences that match consensus sequences poorly, meaning they deviate from the typical sequence patterns that are recognized by RNA polymerase and transcription factors. The other options are not necessarily true for all weak promoters. Some weak promoters may have no consensus sequences, but others may have some. Similarly, some weak promoters may lack a TATA box or -35 region, but others may contain one or both of these elements.

Question 4

A consensus sequence
A)may be a hypothetical sequence.
B)indicates the nucleotides most commonly found at each position.
C)describes the most efficient promoter sequence for the RNA polymerase holoenzyme.
D)All of the above.

Accepted Answer

A consensus sequence can be hypothetical, but it is typically derived from multiple sequences and represents the nucleotides most commonly found at each position. In some cases, a consensus sequence may also represent the most efficient promoter sequence for the RNA polymerase holoenzyme. Therefore, all of the choices are correct.

Question 5

Which is not a property of RNA polymerase?
A)Polymerizes in the 5' → 3' direction.
B)Catalyzes the formation of phosphodiester linkages.
C)Polymerizes a reaction assisted by pyrophosphate hydrolysis.
D)Has exonuclease proof-reading activity.

Accepted Answer

RNA polymerase lacks exonuclease proof-reading activity. This is in contrast to DNA polymerase, which has both 3' → 5' exonuclease proof-reading activity and 5' → 3' polymerase activity.

Question 6

Transcription termination
A)occurs at certain DNA sequences where the elongation complex is unstable.
B)sometimes requires a specific protein,rho,which facilitates disassembly.
C)often occurs near pause sites.
D)All of the above.

Accepted Answer

Transcription termination can occur at certain DNA sequences where the elongation complex is unstable, near pause sites, and sometimes requires the protein rho to facilitate disassembly. Therefore, all of the above choices are correct.

Question 7

Genes that encode for proteins that are needed for basic metabolic processes such as glycolysis are called ________ genes.
A)essential
B)housekeeping
C)core
D)cardinal

Accepted Answer

Housekeeping genes are responsible for basic metabolic processes and cellular maintenance. They are required for the normal functioning of all cells in an organism. Essential genes are those that are required for the viability of an organism, and core genes are those that are present in all members of a particular group or lineage. Cardinal genes are those that are essential for the survival and growth of a microorganism under a particular set of conditions.

Question 8

Which of the following is correct?
A)Transcription proceeds in the 5' → 3' direction.
B)The template strand is copied from the 5' end to the 3' end.
C)RNA polymerization proceeds in the 3' → 5' direction.
D)None of the above.

Accepted Answer

Transcription proceeds in the 5' → 3' direction, meaning that the RNA molecule is synthesized by adding nucleotides to the 3' end of the growing RNA chain. The template DNA strand is read and copied in the 3' → 5' direction, resulting in an RNA molecule that has the same sequence as the non-template (coding) strand of DNA but with uracil replacing thymine. RNA polymerization also occurs in the 5' → 3' direction, as the incoming nucleotide triphosphates are added to the 3' end of the RNA chain.

Question 9

When a sequence of double-strand DNA is displayed,
A)the coding strand is written in the 3' → 5' direction.
B)the template strand is written in the 5' → 3' direction.
C)the coding strand is identical to the RNA product.
D)None of the above.

Accepted Answer

The question statement does not provide enough information to determine the correct answer. The directionality and identity of the strands are dependent on the context of the sequence and its function. Therefore, it is not correct to consistently assume that the coding strand is written in the 3' → 5' direction or that the template strand is written in the 5' → 3' direction, nor that the coding strand is always identical to the RNA product. Further information is needed to determine the correct answer.

Question 10

Which states an improper location or activity?
A)RPo-RNA polymerase at a transcription bubble of DNA.
B)RPc-RNA polymerase bound to single-stranded DNA.
C)NusA -helps convert RNA polymerase to an elongation form.
D)s-protein factor aiding promoter binding.

Accepted Answer

RNA polymerase binds to double-stranded DNA, not single-stranded DNA. Therefore, RPc-RNA polymerase bound to single-stranded DNA is an improper location or activity.

Answer: None of the other choices are improper locations or activities.

Therefore, the answer is B.

Question 11

Which of the following are correct matches for the given genes?
A)rpoN : nitrogen metabolism.
B)rpoH : heat shock.
C)Gene 55 : bacteriophage T4.
D)All of the above.

Accepted Answer

All of the given matches are correct:
- rpoN (also known as sigma54) is associated with regulation of genes involved in nitrogen metabolism.
- rpoH (or sigma32) is involved in the regulation of heat shock genes.
- Gene 55 is a gene found in bacteriophage T4.

Question 12

The sigma-70 subunit
A)increases the affinity of the core polymerase for nonpromoter sequences.
B)decreases the affinity of the core polymerase for specific promoter sequences.
C)is responsible for transcribing many genes.
D)is associated with a holoenzyme,enabling the formation of more stable complexes.
E)All of the above.

Accepted Answer

The sigma-70 subunit is associated with a holoenzyme, which contains the core polymerase and enables the formation of more stable complexes. This stabilizes the interaction between the RNA polymerase and the promoter sequences, leading to efficient transcription initiation. The sigma-70 subunit does not usually affect the affinity of the core polymerase for non-promoter sequences, nor does it decrease the affinity of the core polymerase for specific promoter sequences. While sigma-70 is responsible for transcribing many genes, this function is not directly related to its role in stabilizing the holoenzyme.

Question 13

The type of RNA that is least stable in cells is ________.
A)tRNA
B)rRNA
C)mRNA
D)small RNA

Accepted Answer

mRNA is the least stable type of RNA because it is constantly being synthesized and degraded in cells, with an average half-life of only a few hours. In contrast, tRNA and rRNA are more stable because they have important structural roles in the cell and are not constantly being synthesized and degraded. Small RNA molecules are also generally more stable than mRNA because they are specialized molecules that have specific functions, such as gene regulation.

Question 14

RNA polymerase uses the ________ strand of DNA in transcription.
A)sense
B)antisense
C)coding
D)uncoded

Accepted Answer

RNA polymerase uses the antisense strand of DNA in transcription, also known as the template strand. This is because RNA is synthesized in the 5' to 3' direction, and the RNA molecule must base-pair with the antisense strand to form a complementary sequence. The sense strand, or coding strand, has the same sequence as the RNA molecule, except that thymine is replaced with uracil. However, the RNA polymerase does not use this strand as a template.

Question 15

Two types of ________ RNA are miRNA and siRNA.
A)transfer
B)ribosomal
C)messenger
D)regulatory

Accepted Answer

miRNA (microRNA) and siRNA (short interfering RNA) are both types of regulatory RNA, which play important roles in gene expression regulation. Transfer RNA (tRNA) is involved in protein synthesis, ribosomal RNA (rRNA) is a component of the ribosome, and messenger RNA (mRNA) carries genetic information from DNA to the ribosome during protein synthesis.

Question 16

Which of the following is true for the unwinding of the DNA helix and the synthesis of a short stretch of RNA?
A)The process requires a helicase and a primase as in DNA replication.
B)In transcription,these steps proceed via an RNA polymerase holoenzyme.
C)The unwinding and subsequent synthesis above serve as a primer for chain elongation.
D)All of the above.

Accepted Answer

The answer of Which of the following is true for...

Question 17

What does it mean to say that the most common type of promoter in E.coli is bipartite?
A)The promoter region is divided into two parts which flank the sequence for the gene.
B)There are two separate regions of sequence similarity in the promoter.
C)The sequence of the promoter has dyad symmetry.
D)The promoter must bind two RNA polymerase holoenzymes to transcribe the gene.

Accepted Answer

A bipartite promoter has two regions of sequence similarity, one upstream of the transcription start site and one downstream, which facilitates efficient binding of RNA polymerase to initiate transcription. This is in contrast to a simple promoter where there is only one region of similarity.

Question 18

Which of the following is/are incorrect?
A)tRNAs are extremely stable molecules.
B)Eukaryotic mRNA is highly stable.
C)Bacterial mRNA is not rapidly degraded.
D)All of the above.

Accepted Answer

The answer of Which of the following is/are incorrect?
A)tRNAs are...

Question 19

Which of the following is true about transcription?
A)Promoters are regions of DNA which serve as transcription initiation sites.
B)Initiation is the rate-limiting step in transcription.
C)Each gene,in eukaryotic cells,usually has its own promoter.
D)All of the above.

Accepted Answer

A) Promoters are essential regions of DNA that serve as transcription initiation sites, and are a crucial element of transcription regulation.
B) Initiation is usually the rate-limiting step in transcription, as it involves the recruitment of transcription factors and RNA polymerase to the promoter region.
C) In eukaryotic cells, each gene generally has its own promoter that is specific for that particular gene. This enables the precise regulation of gene expression by controlling the initiation of transcription at individual promoters.

Question 20

The template strand of DNA is copied by RNA polymerase from
A)both 3' → 5' and 5' → 3' ends.
B)5-10 nucleotides before the +1 transition site.
C)3' → 5' end.
D)5' → 3' end.

Accepted Answer

RNA polymerase copies the template strand of DNA from the 3' → 5' end, allowing the synthesis of RNA in the 5' → 3' direction.

Quiz 21: Transcription and RNA Processing

Which statement about RNA polymerase is false?

Which subunit of the E.coli core RNA polymerase (a2bb'w) contributes to DNA binding?

Weak promoters contain

A consensus sequence

Which is not a property of RNA polymerase?

Transcription termination

Genes that encode for proteins that are needed for basic metabolic processes such as glycolysis are called ________ genes.

Which of the following is correct?

When a sequence of double-strand DNA is displayed,

Which states an improper location or activity?

Which of the following are correct matches for the given genes?

The sigma-70 subunit

The type of RNA that is least stable in cells is ________.

RNA polymerase uses the ________ strand of DNA in transcription.

Two types of ________ RNA are miRNA and siRNA.

Which of the following is true for the unwinding of the DNA helix and the synthesis of a short stretch of RNA?

What does it mean to say that the most common type of promoter in E.coli is bipartite?

Which of the following is/are incorrect?

Which of the following is true about transcription?

The template strand of DNA is copied by RNA polymerase from