Deck 17: Transcription, Rna Processing, and Translation

Question 1

Which of the following processes is central to the initiation of transcription?

A) formation of a DNA primer
B) binding of DNA polymerase to the promoter region
C) formation of a phosphodiester bond in the elongating RNA strand
D) binding of sigma to the promoter region

Answer 1

D

Question 2

A primary transcript in the nucleus of a eukaryotic cell is the functional mRNA, while a primary transcript in a prokaryotic cell is _ the functional mRNA.

A) the same size as; larger than
B) larger than; the same size as
C) larger than; smaller than
D) the same size as; the same size as

Answer 2

B

Question 3

In eukaryotic cells, transcription cannot begin until which of the following occurs?

A) The two DNA strands have completely separated and exposed the promoter.
B) The DNA introns are removed from the template.
C) DNA nucleases have isolated the transcription unit.
D) Several transcription factors have bound to the promoter.
E) The 5' caps are removed from the mRNA.

Answer 3

D

Question 4

As scientists were unraveling the mysteries associated with transcription and translation, they discovered there was not a one- to- one correspondence between nucleotide sequence of a gene and base sequence of the mRNA it codes for. They proposed the genes- in- pieces hypothesis. How can the genes- in- pieces hypothesis be explained?

A) Introns are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing.
B) Several related genes are found in the genomes of humans and other animals.
C) Introns are noncoding segments of DNA that are not read or transcribed by RNA polymerase II.
D) Exons are noncoding segments of DNA that are not read or transcribed by RNA polymerase II.

Question 5

Death cap mushrooms produce a substance called - amanitin. a- amanitin efficiently blocks synthesis of mRNA, but not of tRNA or rRNA in eukaryotic organisms. How is that possible?

A) a- amanitin efficiently interferes with RNA polymerase III, but not RNA polymerase I and II.
B) a- amanitin efficiently interferes with the action of RNA polymerase II, but not RNA polymerase I or III.
C) a- amanitin efficiently interferes with the action of RNA polymerase I, but not RNA polymerase II or III.
D) a- amanitin efficiently blocks the action of one or more basic transcription factors.

Question 6

What molecule is responsible for the catalytic activity in the spliceosomes that are involved in removal of introns?

A) proteins of the spliceosome
B) ribozymes
C) RNA polymerase
D) autocatalysis by introns

Question 7

David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters the - 10 box and the - 35 box). What is the function of these two regions of the promoter?

A) They signal the initiation site.
B) They separate the two DNA strands.
C) They bind the sigma subunit that is associated with RNA polymerase.
D) They attach the correct nucleotide triphosphate to the template DNA strand.

Question 8

a- amanitin is a toxin produced by the death cap mushroom. It blocks the synthesis of mRNA. What effect would it have on health of the organism that ate death cap mushrooms?

A) It would block DNA synthesis.
B) It would denature existing proteins.
C) It would tie up Mg²⁺ and, through this action, inhibit glycolysis.
D) It would cause death.

Question 9

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed the mRNA's 5' cap and poly- A tail. Which of the following would you expect her to find?

A) The molecule is digested by enzymes because it is not protected at the 5' end.
B) The mRNA attaches to a ribosome and is translated, but more slowly.
C) The mRNA would not be translated.
D) The mRNA is quickly converted into a ribosomal subunit.
E) The cell adds a new poly- A tail to the mRNA.

Question 10

Which molecule or reaction supplies the energy for polymerization of nucleotides in the process of transcription?

A) ATP only
B) the interaction between RNA polymerase and the promoter
C) the phosphate bonds in the nucleotide triphosphates that serve as substrates
D) the energy released when hydrogen bonds are broken as the DNA molecule is unwound

Question 11

Figure 17.1

-The enzyme complex associated with DNA in the figure is

A) RNA polymerase.
B) topoisomerase.
C) helicase.
D) DNA polymerase.

Question 12

Eukaryotes have three nuclear RNA polymerases. The primary function of RNA polymerase II is

A) transcription of only tRNA- coding genes.
B) transcription of only rRNA- coding genes.
C) transcription of both rRNA- and tRNA- coding genes.
D) transcription of protein- coding genes.

Question 13

How are RNA hairpin turns related to termination?

A) Release factors bind to sites on the hairpin turn, causing release of the RNA transcript.
B) The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.
C) The hairpin turn prevents more nucleoside triphosphates from entering the active site of the enzymes, effectively shutting off the process of polymerization.
D) A three- base repeat signals a stop sequence, and the RNA transcript is released.

Question 14

There should be a strong positive correlation between the rate of protein synthesis and

A) the size of the genome.
B) the number of ribosomes.
C) the size of mRNA.
D) the quantity of DNA polymerase.

Question 15

$\text {Genes and RNA transcripts differ in length.}$
Figure 17.2

-Refer to Figure 17.2. The mRNA is smaller than the length of the DNA that codes for it because

A) post- transcriptional modification removes the exons.
B) the regulatory regions introns) of the gene are not transcribed.
C) post- transcriptional modification removes the introns.
D) bases are added to the tail of the primary transcript.

Question 16

RNA polymerase needs a subunit to initiate transcription that is not needed for transcript elongation. What is the subunit?

A) sigma
B) Mg²⁺
C) rho
D) the holoenzyme

Question 17

Transcription would not occur at the appropriate initiation sites in E. coli if RNA polymerase is missing which of the following?

A) mRNA
B) amino acids
C) the core enzyme
D) sigma

Question 18

The segments of DNA where transcription begins have a binding site for RNA polymerase. These segments are known as

A) initiation factors.
B) promoters.
C) the holoenzyme.
D) sigma.

Question 19

Put the following events of transcription in chronological order.
1) Sigma binds to the promoter region.
2) The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands.
3) Sigma binds to RNA polymerase.
4) Sigma is released.
5) Transcription begins.

A) 3, 2, 1, 4, 5
B) 2, 3, 4, 5, 1
C) 2, 3, 1, 4, 5
D) 3, 1, 2, 5, 4

Question 20

During elongation, RNA polymerase has three prominent channels, or grooves. These channels provide sites for all of the following, EXCEPT

A) a site for the entry of ribonucleoside triphosphates.
B) a site for the exit of the diphosphates removed from the nucleotide triphosphates.
C) a site for the growing RNA strand.
D) a site for the double- stranded DNA molecule.

Question 21

How does termination of translation take place?

A) The ribosome reaches the end of the mRNA molecule.
B) Stop codons with no corresponding tRNAs are read.
C) Energy depletion causes termination.
D) Hairpin turns of mRNA force the ribosome off the molecule.

Question 22

Ribosomes can attach to prokaryotic messenger RNA

A) once replication is complete.
B) once post- transcriptional modification is complete.
C) once the primary transcript has been released from RNA polymerase.
D) before transcription is complete.

Question 23

Figure 17.3
Refer to Figure 17.3. What is the function of the AGU on the loop of the tRNA?

A) It is the active site of this ribozyme.
B) It base pairs with the codon of mRNA.
C) It stabilizes the tRNA- amino acid complex.
D) It attaches to the amino acid.

Question 24

Which of the following is NOT one of the steps in initiation of translation?

A) binding of tRNA carrying formyl methionine to the start codon and small ribosomal subunit
B) recognition and binding of mRNA by the small ribosomal subunit
C) binding of the large ribosomal subunit to the small ribosomal subunit
D) formation of a polypeptide bond

Question 25

There are 61 codons that each specify the addition of a specific amino acid, and three stop codons for which there is no corresponding amino acid. However, there are only about 40 tRNA molecules, representing 40 anticodons. How is that possible?

A) An anticodon forms hydrogen bonds with the codon; it must match the first two bases of the codon, but is less specific with respect to the third base.
B) Only about 40 of the recognized 61 codons are present in mRNA.
C) There are tRNAs that can bind one of two related amino acids.
D) Only 20 of the codons are active-one for each amino acid.

Question 26

A part of an mRNA molecule with the following sequence is being read by a ribosome:
5' CCG- ACG 3'mRNA). The following charged transfer RNA molecules with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form.
Table 17.1
$\begin{array} { | l | l | } \hline \text { tRNA Anticodon } & \text { Anind Acid } \\\hline \text { FRE } & \text { Prolire } \\\text { CEW } & \text { Alanire } \\\text { WEE } & \text { Thronire } \\\text { EEE } & \text { Glycire } \\\text { AEE } & \text { Cyateine } \\\text { EEE } & \text { Alanire } \\\hline\end{array}$
What is the anticodon loop of the first tRNA that will complement this mRNA?

A) 3' UGC 5'
B) 3' GGC 5'
C) 5' GGC 3'
D) 5' UGC 3'
E) 5' ACG 3'

Question 27

A transfer RNA #1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing poly on the other tRNA #2) in the ribosome already.
Where does tRNA #2 move to after this bonding of lysine to the polypeptide?

A) A site
B) directly to the cytosol
C) E site
D) exit tunnel
E) P site

Question 28

The ribosome- binding site of prokaryotes is also known as

A) the promoter.
B) the Pribnow box.
C) the Shine- Dalgarno sequence.
D) the TATA box.

Question 29

Figure 17.4
Refer to Figure 17.4. During elongation, which site in the ribosome represents the location where a codon is being read?

A) P site
B) small subunit
C) E site
D) A site

Question 30

Post- translational modifications include all of the following EXCEPT

A) formation of covalent bonds between cysteine residues of the amino acid site chains.
B) removal of introns.
C) addition of carbohydrates to form a glycoprotein.
D) formation of hydrogen bonds among carbonyl and amino groups of the polypeptide backbone.

Question 31

Which of the following occurs in prokaryotes, but not eukaryotes?

A) gene regulation
B) translation in the absence of a ribosome
C) concurrent transcription and translation
D) post- transcriptional splicing

Question 32

Once a peptide has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, which process on the list occurs next?

A) initiation
B) translocation
C) reading of the next codon of mRNA
D) the codon- anticodon hydrogen bonds holding the tRNA in the A site are broken

Question 33

What is the function of the 3' end of the tRNA?

A) It is the active site of this ribozyme.
B) It stabilizes the tRNA- amino acid complex.
C) It base pairs with the codon of mRNA.
D) It attaches to the amino acid.

Question 34

The start codon is the same for prokaryotes and eukaryotes. What is the start codon?

A) AUG
B) an anticodon
C) a ribozyme
D) GGC

Question 35

Which of the following does not play a role in the process of translation?

A) ATP
B) exons
C) GTP
D) tRNAs
E) 5' G- cap

Question 36

A mutant bacterial cell has a defective aminoacyl- tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. What would the consequence of this be for the cell?

A) None of the proteins in the cell will contain phenylalanine.
B) The ribosome will skip a codon every time a UUU is encountered.
C) The cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine- specifying anticodons.
D) Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
E) The ribosome will stall whenever an abnormal lysine tRNA binds to the A site.

Question 37

Put the following events of elongation in prokaryotic translation in chronological order.
1) Binding of mRNA with small ribosomal subunit.
2) Recognition of initiation codon
3) Complementary base pairing between initiator codon and anticodon of initiator tRNA
4) Base pairing of the mRNA codon following the initiator codon with its complementary tRNA
5) Attachment of the large subunit

A) 1, 2, 3, 4, 5
B) 2, 1, 4, 3, 5
C) 1, 2, 3, 5, 4
D) 5, 4, 3, 2, 1