Question 1

The enzyme RNA polymerase synthesizes a specific RNA when provided with which of the following as a template?
A) Soluble RNA
B) Ribosomal RNA
C) Messenger RNA
D) Single-stranded DNA
E) Double-stranded DNA

Accepted Answer

RNA polymerase synthesizes RNA using a double-stranded DNA molecule as a template. The enzyme unwinds the double helix, reads the template strand, and synthesizes a complementary RNA molecule. The other answer choices (soluble RNA, ribosomal RNA, and messenger RNA) are types of RNA that are synthesized by different mechanisms and do not serve as templates for RNA polymerase. Single-stranded DNA is not a suitable template because it lacks a complementary strand for the enzyme to read.

Question 2

In a comparison of typical eukaryotic and prokaryotic mRNA, all of the following are true EXCEPT
A) the termini at the 5' end differ.
B) the termini at the end differ.
C) both contain regions which are not translated.
D) both may be translated before transcription is completed.
E) AUG is an initiation codon for translation in both.

Accepted Answer

Prokaryotic mRNA can be translated as it is being transcribed, a process called coupled transcription-translation, whereas eukaryotic mRNA must undergo post-transcriptional processing and be transported out of the nucleus before translation can occur. Therefore, statement D is false. The other statements are true.

Question 3

All of the following statements about the RNA polymerase are true EXCEPT which one?
A) RNA polymerase requires nucleoside triphosphates as substrates.
B) The 5'-end of the synthesized RNA contains a triphosphate.
C) The product is covalently linked to the template.
D) The product is of a specific base sequence dictated by the template.

Accepted Answer

RNA polymerase synthesizes RNA by using a DNA template, but the product (RNA) is not covalently linked to the DNA template. The RNA strand is synthesized complementary to the DNA template strand and is released once the transcription is complete.

Question 4

Small nuclear RNAs such as U1, U2 and U5 affect gene expression by
A) diminishing the rate of transcription.
B) functioning as modified bases within tRNA.
C) functioning as self-catalytic components of rRNA.
D) functioning as essential components of the spliceosome.
E) promoting proper transcription termination.

Accepted Answer

Small nuclear RNAs U1, U2 and U5 function as essential components of the spliceosome, which is responsible for removing introns and splicing exons together to form mature mRNA. Therefore, they play a crucial role in regulating gene expression by influencing mRNA splicing.

Question 5

Splicing of eukaryotic mRNA precursors involves all of the following EXCEPT
A) binding of small nuclear RNAs.
B) binding of poly(A) polymerase.
C) assembly of spliceosome.
D) RNA cleavage and ligation reactions.

Accepted Answer

Although poly(A) polymerase is involved in the processing of mRNA, it is not directly involved in splicing of the mRNA precursor. The other answer choices are all involved in the splicing process.

Question 6

RNA polymerases in eukaryotic cells
A) are localized in the post-mitochondrial cytoplasmic fraction.
B) require DNA replication to function.
C) exist in multiple molecular forms which have different specificities.
D) require a primer for chain elongation.
E) polymerize RNA chains in the to 5' direction.

Accepted Answer

RNA polymerases in eukaryotic cells exist in multiple molecular forms, referred to as RNA polymerase I, II, and III. These different polymerases have different specificities for different types of RNA molecules. For example, RNA polymerase II is responsible for transcribing protein-coding genes, while RNA polymerase III transcribes genes for tRNAs, 5S rRNA, and some other small RNA molecules.

Question 7

A characteristic of transcription by RNA polymerase II in eukaryotic cells is:
A) the absence of promoters elements.
B) translation initiation prior to transcription termination.
C) translation termination prior to transcription termination.
D) covalent addition of nucleotide(s) that are not encoded by DNA to the 5' and 3' ends of the transcript.
E) constitutive expression of most genes.

Accepted Answer

RNA polymerase II adds a modified nucleotide cap (7-methylguanosine) to the 5' end of the mRNA and a string of 100-250 adenine nucleotides to the 3' end in a process called capping and polyadenylation, respectively. These nucleotides are not encoded by DNA, hence covalent addition of these non-encoded nucleotides occurs during transcription.

Question 8

Many eukaryotic and some prokaryotic genes have their coding regions interrupted by introns (intervening sequences). These intronic sequences are removed
A) during translation.
B) from messenger RNA by polyadenylation.
C) from genomic DNA by nucleases.
D) from heterogeneous nuclear RNA through a process called splicing.
E) from transfer RNA by charging which involves amino acids.

Accepted Answer

Intronic sequences are removed from pre-mRNA (also known as heterogeneous nuclear RNA) by a process called splicing, which results in the formation of mature mRNA that can then undergo translation to produce a functional protein. Introns are not removed during translation, polyadenylation is the addition of a poly-A tail to the 3' end of mRNA and does not affect introns, and nucleases are involved in the degradation of DNA and RNA but not specifically in the removal of introns. Transfer RNA does not typically contain introns.

Question 9

Which ONE of the following nuclear RNA processing events is correct?
A) Many RNA transcripts have a cap of 7-methyl-guanine added to the end of the RNA.
B) The splice sites in precursors to mRNA are initially recognized by an enzyme that marks them by methylation.
C) A poly G tail of up to about 200 guanine residues is added to the end of most pre-mRNA molecules.
D) The 5'-end of many RNAs is capped using a 5'-5' pyrophosphate link.
E) After synthesis of RNA on the DNA template, ribothymidine residues in the RNA are demethylated to uridine residues.

Accepted Answer

The 5'-end of many RNAs is capped with a unique structure involving a 5'-5' triphosphate link to a 7-methylguanosine. This cap structure is critical for RNA stability, export from the nucleus, and translation initiation in eukaryotes. The other options describe processes that do not accurately represent RNA processing events.

Question 10

Splicing of pre-mRNA introns is accomplished by:
A) hydrolysis of two molecules of ATP.
B) hydrolysis of two molecules of GTP.
C) two transesterification reactions.
D) covalent attachment of guanosine to the 5'_end of the exon.
E) covalent attachment of the exon to the intron.

Accepted Answer

Splicing of pre-mRNA introns is accomplished by two transesterification reactions. During the first reaction, the 2'OH group of an adenosine residue within the intron attacks the phosphate at the 5' end of the intron, resulting in the formation of a lariat structure and the release of the 5' exon. During the second reaction, the 3'OH group of the 5' exon attacks the phosphate at the 3' end of the 3' exon, resulting in the release of the intron and the joining of the two exons. No ATP, no GTP, no guanosine, and no covalent attachment of the exon to the intron are involved in the splicing mechanism.

Question 11

Regarding RNA synthesis, which of the following statements is correct?
A) The rho subunit is required for chain initiation.
B) Synthesis of mRNA from a DNA template strand occurs in a 5 ==> direction anti-parallel to the template.
C) The first nucleotide placed in an RNA transcript of prokaryotic cells is GTP and ATP.
D) Both A and B are correct.
E) Both B and C are correct.

Accepted Answer

Choice A is incorrect as the rho subunit is involved in termination of transcription, not initiation. Choice B is correct as RNA polymerase reads the DNA template strand in the 3' to 5' direction and synthesizes the complementary RNA strand in the 5' to 3' direction. Choice C is also correct as the first nucleotides placed in an RNA transcript of prokaryotic cells are GTP and ATP. Therefore, E is the correct answer.

Question 12

Which statement is true?
A) transcription of DNA to RNA initiates at a region of the DNA called a promoter region.
B) Within a given gene, usually one strand of the DNA is copied and then the other is copied into RNA.
C) When DNA or RNA is copied this means that from the DNA sequence GCAGTTA the copy will read GCAGTTA.
D) During DNA synthesis, the primer is copied into RNA but is later removed by an exonuclease.
E) The 5' end of a DNA molecule always has the phosphate.

Accepted Answer

Transcription of DNA to RNA initiates at a region of the DNA called a promoter region. This is where RNA polymerase binds to start transcription.

Question 13

Which of the following is not characteristic of tRNAs?
A) They form extensive secondary structure.
B) They have many modified bases.
C) They are spliced post-transcriptionally.
D) They get nucleotides added to their end post- transcriptionally.
E) They contain the codon for translation.

Accepted Answer

tRNAs do not contain codons; they contain anticodons that pair with the codons on mRNA during the process of translation. Codons are found on mRNA and dictate the amino acid sequence.

Question 14

Genes containing intervening sequences (or introns)
A) are rare in eukaryotic cells.
B) code for mRNA precursors which must be spliced before translation.
C) must undergo a DNA rearrangement before expression.
D) do not code for proteins.
E) are common in prokaryotes.

Accepted Answer

Genes containing intervening sequences, or introns, are common in eukaryotic cells. These introns do not code for proteins but are instead transcribed into mRNA precursors, which must be spliced before translation can occur. This splicing removes the introns and joins together the remaining exons to form a mature mRNA molecule.

Question 15

All of the following statements about RNA polymerase and DNA polymerase are correct EXCEPT
A) both require a template.
B) both require nucleoside triphosphates as substrates.
C) both elongate in the 5' to direction.
D) both require a primer.
E) both are required for replication in certain systems.

Accepted Answer

RNA polymerase does not require a primer to initiate synthesis, whereas DNA polymerase does.

Question 16

The beta-globin gene from a thalassemic patient was cloned and sequenced. The technician who characterized this gene informs you that a point mutation was found, but that it can not account for the thalassemia because the mutation occurred within an intron sequence. What doesn't the technician understand?
A) splicing occurs subsequent to protein synthesis.
B) Introns encode general transcription factors.
C) Intron sequences are required for transcription termination.
D) Intron sequences are required for translation termination.
E) Certain intron sequences are absolute requirements for splicing.

Accepted Answer

The technician doesn't understand that certain intron sequences are absolute requirements for splicing. These sequences are recognized by the spliceosome and are essential for the proper splicing of the pre-mRNA into the mature mRNA. Mutations in these sequences can result in aberrant splicing, which can lead to diseases such as thalassemia. Therefore, even though the mutation occurred within an intron, it could still be responsible for the thalassemia if it disrupted an essential splicing sequence.

Question 17

Leucine zipper domains found in many transcription factors function directly in
A) DNA binding.
B) transactivation.
C) dimerization.
D) zinc binding.

Accepted Answer

Leucine zipper domains are involved in dimerization, which allows the transcription factors to form functional complexes that can bind to DNA and activate transcription.

Question 18

All of the following statements about ribosomes are correct EXCEPT which one?
A) All ribosomes have two subunits, the large subunit approximately twice the size of the smaller subunit.
B) Eukaryotic cells have 80S ribosomes, and protein synthesis on these ribosomes can be inhibited by cycloheximide.
C) Prokaryotic cells have 70S ribosomes, and protein synthesis on these ribosomes can be inhibited by chloramphenicol.
D) Mitochondria have 80S ribosomes, and protein synthesis on these ribosomes can be inhibited by cycloheximide.
E) The larger subunits of all ribosomes have the enzyme peptidyl transferase which forms peptide bonds.

Accepted Answer

Mitochondria have 70S ribosomes, not 80S.

Question 19

Eukaryotic RNA polymerase II differs from the prokaryotic RNA polymerase because it
A) retains sigma factor during elongation.
B) can incorporate either deoxy- or ribonucleotide precursors.
C) requires multiple accessory proteins.
D) transcribes only ribosomal RNA genes.
E) interacts directly with the termination factor rho.

Accepted Answer

Eukaryotic RNA polymerase II requires multiple accessory proteins, whereas prokaryotic RNA polymerase does not.

(Note: A is incorrect because sigma factor is associated with prokaryotic RNA polymerase, not eukaryotic RNA polymerase II. B is incorrect because both prokaryotic and eukaryotic RNA polymerases can incorporate ribonucleotide precursors. D is incorrect because eukaryotic RNA polymerase II transcribes all protein-coding genes, not just ribosomal RNA genes. E is incorrect because termination in eukaryotes is typically mediated by different factors than in prokaryotes; eukaryotic RNA polymerase II interacts with a termination factor called TTF-I.)

Question 20

In what part of the mammalian cell is ribosomal RNA produced?
A) Endoplasmic reticulum
B) Mitochondrion
C) Nucleolus
D) Golgi apparatus

Accepted Answer

Ribosomal RNA is produced in the nucleolus of the mammalian cell. The nucleolus is a specialized organelle within the nucleus where ribosomal RNA is transcribed, processed, and assembled with ribosomal proteins to form ribosomes which are used for protein synthesis.

Quiz 5: RNA: Transcription and Rna Processing

The enzyme RNA polymerase synthesizes a specific RNA when provided with which of the following as a template?

In a comparison of typical eukaryotic and prokaryotic mRNA, all of the following are true EXCEPT

All of the following statements about the RNA polymerase are true EXCEPT which one?

Small nuclear RNAs such as U1, U2 and U5 affect gene expression by

Splicing of eukaryotic mRNA precursors involves all of the following EXCEPT

RNA polymerases in eukaryotic cells

A characteristic of transcription by RNA polymerase II in eukaryotic cells is:

Many eukaryotic and some prokaryotic genes have their coding regions interrupted by introns (intervening sequences) . These intronic sequences are removed

Which ONE of the following nuclear RNA processing events is correct?

Splicing of pre-mRNA introns is accomplished by:

Regarding RNA synthesis, which of the following statements is correct?

Which statement is true?

Which of the following is not characteristic of tRNAs?

Genes containing intervening sequences (or introns)

All of the following statements about RNA polymerase and DNA polymerase are correct EXCEPT

Leucine zipper domains found in many transcription factors function directly in

All of the following statements about ribosomes are correct EXCEPT which one?

Eukaryotic RNA polymerase II differs from the prokaryotic RNA polymerase because it

In what part of the mammalian cell is ribosomal RNA produced?