Deck 7: From DNA to Protein

Question 1

You have a bacterial strain with a mutation that removes the transcription termination signal from the Abd operon.Which of the following statements describes the most likely effect of this mutation on Abd transcription?

A)The Abd RNA will not be produced in the mutant strain.
B)The Abd RNA from the mutant strain will be longer than normal.
C)Sigma factor will not dissociate from RNA polymerase when the Abd operon is being transcribed in the mutant strain.
D)RNA polymerase will move in a backward fashion at the Abd operon in the mutant strain.

Answer 1

B

Question 2

Figure 7-3 shows a ribose sugar.The part of the ribose sugar where a new ribonucleotide will attach in an RNA molecule is pointed to by arrow Figure 7-3

A)1.
B)3.
C)4.
D)5.

Answer 2

C

Question 3

Which of the following statements is FALSE?

A)RNA polymerase can start making a new RNA molecule without a primer; DNA polymerase cannot.
B)RNA polymerase does not proofread its work; DNA polymerase does.
C)RNA polymerase catalyzes the linkage of ribonucleotides while DNA polymerase catalyzes the linkage of deoxyribonucleotides.
D)RNA polymerase adds bases in a 3′-to-5′ direction; DNA polymerase adds bases in a 5′-to-3′ direction.

Answer 3

D

Question 4

Transcription in bacteria differs from transcription in a eukaryotic cell because

A)RNA polymerase (along with its sigma subunit) can initiate transcription on its own.
B)RNA polymerase (along with its sigma subunit) requires the general transcription factors to assemble at the promoter before polymerase can begin transcription.
C)the sigma subunit must associate with the appropriate type of RNA polymerase to produce mRNAs.
D)RNA polymerase must be phosphorylated at its C-terminal tail for transcription to proceed.

Question 5

Consider two genes that are next to each other on a chromosome, as arranged in Figure 7-1. Figure 7-1
Which of the following statements is TRUE?

A)The two genes must be transcribed into RNA using the same strand of DNA.
B)If gene A is transcribed in a cell, gene B cannot be transcribed.
C)Gene A and gene B can be transcribed at different rates, producing different amounts of RNA within the same cell.
D)If gene A is transcribed in a cell, gene B must be transcribed.

Question 6

Figure 7-3 shows a ribose sugar.RNA bases are added to the part of the ribose sugar pointed to by arrow Figure 7-3

A)3.
B)4.
C)5.
D)6.

Question 7

Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon?

A)Eukaryotes have three types of RNA polymerase.
B)Eukaryotic RNA polymerases require general transcription factors.
C)The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter.
D)Prokaryotic genes are packaged into nucleosomes.

Question 8

Transcription is similar to DNA replication in that

A)an RNA transcript is synthesized discontinuously and the pieces are then joined together.
B)it uses the same enzyme as that used to synthesize RNA primers during DNA replication.
C)the newly synthesized RNA remains paired to the template DNA.
D)nucleotide polymerization occurs only in the 5′-to-3′ direction.

Question 9

There are several reasons why the primase used to make the RNA primer for DNA replication is not suitable for gene transcription.Which of the statements below is NOT one of those reasons?

A)Primase initiates RNA synthesis on a single-stranded DNA template.
B)Primase can initiate RNA synthesis without the need for a base-paired primer.
C)Primase synthesizes only RNAs of about 5-20 nucleotides in length.
D)The RNA synthesized by primase remains base-paired to the DNA template.

Question 10

Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing?

A)5′-CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′
B)5′-UGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUG-3′
C)5′-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-3′
D)5′-GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3′

Question 11

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes.This is largely because RNA

A)contains uracil and uses ribose as the sugar.
B)bases cannot form hydrogen bonds with each other.
C)nucleotides use a different chemical linkage between nucleotides compared to DNA.
D)is single-stranded.

Question 12

RNA in cells differs from DNA in that

A)it contains the base uracil, which pairs with cytosine.
B)it is single-stranded and cannot form base pairs.
C)it is single-stranded and can fold up into a variety of structures.
D)the sugar ribose contains fewer oxygen atoms than does deoxyribose.

Question 13

Which of the following statements is FALSE?

A)A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule's synthesis is completed.
B)If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies.
C)RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides.
D)Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.

Question 14

You have a piece of DNA that includes the following sequence:
5′-ATAGGCATTCGATCCGGATAGCAT-3′
3′-TATCCGTAAGCTAGGCCTATCGTA-5′
Which of the following RNA molecules could be transcribed from this piece of DNA?

A)5′-UAUCCGUAAGCUAGGCCUAUGCUA-3′
B)5′-AUAGGCAUUCGAUCCGGAUAGCAU-3′
C)5′-UACGAUAGGCCUAGCUUACGGAUA-3′
D)none of these answers are correct.

Question 15

Which of the following might decrease the transcription of only one specific gene in a bacterial cell?

A)a decrease in the amount of sigma factor
B)a decrease in the amount of RNA polymerase
C)a mutation that introduced a stop codon into the DNA that precedes the gene's coding sequence
D)a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site

Question 16

The sigma subunit of bacterial RNA polymerase

A)contains the catalytic activity of the polymerase.
B)remains part of the polymerase throughout transcription.
C)recognizes promoter sites in the DNA.
D)recognizes transcription termination sites in the DNA.

Question 17

Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads to which the polynucleotide 5′-TTTTTTTTTTTTTTTTTTTTTTTTT-3′ has been covalently attached.After a short incubation, the beads are then extracted from the mixture.When you analyze the cellular nucleic acids that have stuck to the beads, which of the following is most abundant?

A)DNA
B)tRNA
C)rRNA
D)mRNA

Question 18

You have a segment of DNA that contains the following sequence:
5′-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3′
3′-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5′
You know that the RNA transcribed from this segment contains the following sequence:
5′-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3′
Which of the following choices best describes how transcription occurs?

A)The top strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′.
B)The top strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′.
C)The bottom strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′.
D)The bottom strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′.

Question 19

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?

A)The ribosome binds to the mRNA.
B)The mRNA is polyadenylated at its 3′ end.
C)A guanine nucleotide with a methyl group is added to the 5′ end of the mRNA.
D)RNA polymerase dissociates.

Question 20

Figure 7-3 shows a ribose sugar.The part of the ribose sugar that is different from the deoxyribose sugar used in DNA is pointed to by arrow Figure 7-3

A)1.
B)4.
C)5.
D)6.

Question 21

Which of the following statements about RNA splicing is FALSE?

A)Conventional introns are not found in bacterial genes.
B)For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene.
C)Small RNA molecules in the nucleus perform the splicing reactions necessary for the removal of introns.
D)Splicing occurs after the 5′ cap has been added to the end of the primary transcript.

Question 22

Genes in eukaryotic cells often have intronic sequences coded for within the DNA.These sequences are ultimately not translated into proteins.Why?

A)Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus.
B)Introns are not transcribed by RNA polymerase.
C)Introns are removed by catalytic RNAs in the cytoplasm.
D)The ribosome will skip over intron sequences when translating RNA into protein.

Question 23

Which of the following statements about the genetic code is CORRECT?

A)All codons specify more than one amino acid.
B)The genetic code is redundant.
C)All amino acids are specified by more than one codon.
D)All codons specify an amino acid.

Question 24

The ribosome is important for catalyzing the formation of peptide bonds.Which of the following statements is TRUE?

A)The number of rRNA molecules that make up a ribosome greatly exceeds the number of protein molecules found in the ribosome.
B)The large subunit of the ribosome is important for binding to the mRNA.
C)The catalytic site for peptide bond formation is formed primarily from an rRNA.
D)Once the large and small subunits of the ribosome assemble, they will not separate from each other until degraded by the proteasome.

Question 25

Below is the sequence from the 3? end of an mRNA.
5?-CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3? $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$
Table 7-29
If you were told that this sequence contains the stop codon for the protein encoded by this mRNA, what is the anticodon on the tRNA in the P site of the ribosome when release factor binds to the A site?

A)5?-CCA-3?
B)5?-CCG-3?
C)5?-UGG-3?
D)5?-UUA-3?

Question 26

What do you predict would happen if you created a tRNA with an anticodon of 5?-CAA-3? that is charged with methionine, and added this modified tRNA to a cell-free translation system that has all the normal components required for translating RNAs? $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$ Table 7-29

A)Methionine would be incorporated into proteins at some positions where glutamine should be.
B)Methionine would be incorporated into proteins at some positions where leucine should be.
C)Methionine would be incorporated into proteins at some positions where valine should be.
D)Translation would no longer be able to initiate.

Question 27

A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5′-AUGAAAAAAAAAAAAUAA-3′ has the following effect: the only product made is a Met-Lys dipeptide that remains attached to the ribosome.What is the most likely way in which the poison acts to inhibit protein synthesis?

A)It inhibits peptidyl transferase activity.
B)It inhibits movement of the small subunit relative to the large subunit.
C)It inhibits release factor.
D)It mimics release factor.

Question 28

Which amino acid would you expect a tRNA with the anticodon 5?-CUU-3? to carry? $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$ Table 7-29

A)lysine
B)glutamic acid
C)leucine
D)phenylalanine

Question 29

A mutation in the tRNA for the amino acid lysine results in the anticodon sequence 5?-UAU-3? (instead of 5?-UUU-3?).Which of the following aberrations in protein synthesis might this tRNA cause? $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$ Table 7-29

A)read-through of stop codons
B)substitution of lysine for isoleucine
C)substitution of lysine for tyrosine
D)substitution of lysine for phenylalanine

Question 30

You have discovered a protein that inhibits translation.When you add this inhibitor to a mixture capable of translating human mRNA and centrifuge the mixture to separate polyribosomes and single ribosomes, you obtain the results shown in Figure 7-39.Which of the following interpretations is consistent with these observations? Figure 7-39

A)The protein binds to the small ribosomal subunit and increases the rate of initiation of translation.
B)The protein binds to sequences in the 5′ region of the mRNA and inhibits the rate of initiation of translation.
C)The protein binds to the large ribosomal subunit and slows down elongation of the polypeptide chain.
D)The protein binds to sequences in the 3′ region of the mRNA and prevents termination of translation.

Question 31

Which of the following statements about prokaryotic mRNA molecules is FALSE?

A)A single prokaryotic mRNA molecule can be translated into several proteins.
B)Ribosomes must bind to the 5′ cap before initiating translation.
C)mRNAs are not polyadenylated.
D)Ribosomes can start translating an mRNA molecule before transcription is complete.

Question 32

You have discovered a gene (Figure 7-28A) that is alternatively spliced to produce several forms of mRNA in various cell types, three of which are shown in Figure 7-28B.The lines connecting the exons that are included in the mRNA indicate the splicing.From your experiments, you know that protein translation begins in exon 1.For all forms of the mRNA, the encoded protein sequence is the same in the regions of the mRNA that correspond to exons 1 and 10.Exons 2 and 3 are alternative exons used in different mRNA, as are exons 7 and 8.Which of the following statements about exons 2 and 3 is the most accurate? (A)


(B)

Figure 7-28

A)Exons 2 and 3 must have the same number of nucleotides.
B)Exons 2 and 3 must contain an integral number of codons (that is, the number of nucleotides divided by 3 must be an integer).
C)Exons 2 and 3 must contain a number of nucleotides that when divided by 3, leaves the same remainder (that is, 0, 1, or 2).
D)Exons 2 and 3 must have different numbers of nucleotides.

Question 33

Which of the following pairs of codons might you expect to be read by the same tRNA as a result of wobble? $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$ Table 7-29

A)CUU and UUU
B)GAU and GAA
C)CAC and CAU
D)AAU and AGU

Question 34

Which of the following statements is TRUE?

A)Ribosomes are large RNA structures composed solely of rRNA.
B)Ribosomes are synthesized entirely in the cytoplasm.
C)rRNA contains the catalytic activity that joins amino acids together.
D)A ribosome binds one tRNA at a time.

Question 35

The concentration of a particular protein, X, in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply.The level of its mRNA in the cell remains fairly constant throughout this time.Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed.You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal.Which of the following mutations in the gene for X could explain these results?

A)the introduction of a stop codon that truncates protein X at the fourth amino acid
B)a change of the first ATG codon to CCA
C)the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein
D)a change at a splice site that prevents splicing of the RNA

Question 36

In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by

A)binding directly to a ribosome-binding site preceding the initiation codon.
B)scanning along the mRNA from the 5′ end.
C)recognizing an AUG codon as the start of translation.
D)binding an initiator tRNA.

Question 37

The piece of RNA below includes the region that codes for the binding site for the initiator tRNA needed in translation.
5?-GUUUCCCGUAUACAUGCGUGCCGGGGGC-3? $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$
Table 7-29
Which amino acid will be on the tRNA that is the first to bind to the A site of the ribosome?

A)methionine
B)arginine
C)cysteine
D)valine

Question 38

Which of the following statements is FALSE?

A)Information determining the lifetimes of mRNA molecules is encoded in the nucleotide sequences of the mRNA molecule.
B)An mRNA molecule in bacteria will typically have a shorter lifetime compared to an mRNA molecule in a eukaryotic cell.
C)Eukaryotic mRNA molecules do not have lifetimes longer than 30 minutes.
D)mRNA molecules are degraded into nucleotides by ribonucleases in the cytosol.

Question 39

snRNAs

A)are translated into snRNPs.
B)are important for producing mature mRNA transcripts in bacteria.
C)are removed by the spliceosome during RNA splicing.
D)can bind to specific sequences at intron-exon boundaries through complementary base-pairing.

Question 40

A strain of yeast translates mRNA into protein inaccurately.Individual molecules of a particular protein isolated from this yeast have variations in the first 11 amino acids compared with the sequence of the same protein isolated from normal yeast cells, as listed in Figure 7-33.What is the most likely cause of this variation in protein sequence? $\begin{array}{c}\begin{array}{lll}\text {normal sequence}\\\\\text {variants}\\\\\\\\\\\\\end{array}\begin{array}{lll} \text {Met}\\\\ \text {Met}\\ \text {Met}\\ \text {Met}\\ \text {Met}\\ \text {Met}\\ \text {Met}\end{array}\begin{array}{lll} \text {Thr}\\\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\end{array}\begin{array}{lll} \text {Ala}\\\\ \text {Ala}\\ \text {Ala}\\ \text {Ala}\\ \text {Ala}\\ \text {Ala}\\ \text {Ala} \end{array}\begin{array}{lll} \text {Ile}\\\\ \text {Ala}\\ \text {Gly}\\ \text {val}\\ \text {Ile}\\ \text {Ile}\\ \text {Ile} \end{array}\begin{array}{lll} \text {Val}\\\\ \text {Val}\\ \text {Val}\\ \text {Val}\\ \text {Val}\\ \text {Val} \\ \text {Va} \end{array}\begin{array}{lll}\text {Ser}\\\\\text {Ser}\\\text {Ser}\\\text {Ser}\\\text {Ser}\\\text {Ser}\\\text {Ser}\end{array}\begin{array}{lll}\text {Asn}\\\\\text {Asn}\\\text {Asn}\\\text {Asn}\\\text {Asn}\\\text {Asn}\\\text {Asn}\end{array}\begin{array}{lll}\text {Thr}\\\\\text {Thr}\\\text {Thr}\\\text {Thr}\\\text {Thr}\\\text {Thr}\\\text {Thr}\end{array}\begin{array}{lll}\text { Gln}\\\\\text { Gln } \\\text { Gln } \\\text { Gln } \\\text { Gln } \\\text { Gln } \\\text { Gln }\end{array}\begin{array}{lll}\text { Ile}\\\\\text { Ile}\\\text { Ile}\\\text { Ile}\\\text { Ala}\\\text { Gly}\\\text { Val}\end{array}\begin{array}{lll}\text {Lys}\\\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\end{array}\end{array}$
Figure 7-33 $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$

Table 7-29

A)a mutation in the DNA coding for the protein
B)a mutation in the anticodon of the isoleucine-tRNA (tRNA^Ile)
C)a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different amino acids
D)a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different tRNA molecules

Question 41

When using a repeating trinucleotide sequence (such as 5′-AAC-3′) in a cell-free translation system, you will obtain

A)three different types of peptides, each made up of a single amino acid.
B)peptides made up of three different amino acids in random order.
C)peptides made up of three different amino acids, each alternating with each other in a repetitive fashion.
D)polyasparagine, as the codon for asparagine is AAC.

Question 42

In a diploid organism, the DNA encoding one of the tRNAs for the amino acid tyrosine is mutated such that the sequence of the anticodon is now 5′-CTA-3′ instead of 5′-GTA-3′.What kind of aberration in protein synthesis will this tRNA cause? Explain your answer.
Table 7-29

Question 43

Ribozymes are known to catalyze which of the following reactions in cells?

A)DNA synthesis
B)transcription
C)RNA splicing
D)protein hydrolysis

Question 44

You have discovered an alien life-form that surprisingly uses DNA as its genetic material, makes RNA from DNA, and reads the information from RNA to make protein using ribosomes and tRNAs, which read triplet codons.Because it is your job to decipher the genetic code for this alien, you synthesize some artificial RNA molecules and examine the protein products produced from these RNA molecules in a cell-free translation system using purified alien tRNAs and ribosomes.You obtain the results shown in Table 7-48. $\begin{array}{c|c}\text { Message } & \text { Peptides produced } \\\hline \text { poly UA } & \text {... Tyr-Cys-Tyr-Cys ... } \\\hline \text { poly UC } & \text {... Phe-Lys-Phe-Lys .... }\\\text { poly UAC } & \ldots \text { lle-lle-lle-lle ... } \\& +\\&\text {... Ser-Ser-Ser-Ser... } \\&+ \\&\text {... Pro-Pro-Pro-Pro ... }\\\hline\text { poly UCA } & \text {... Ala-Ala-Ala-Ala ... } \\& +\\&\text { ... His-His-His-His...}\\&+\\&\text { ... Val-Val-Val-Val...}\\\hline\text { poly AUA } & \ldots \text { Arg-Arg-Arg-Arg ... } \\& +\\&\text { ... Glu-Glu-Glu-Glu... }\\&+\\&\text { ... Tyr-Tyr-Tyr-Tyr ... }\end{array}$ Table 7-48
From this information, which of the following peptides can be produced from poly UAUC?

A)Ile-Phe-Val-Tyr
B)Tyr-Ser-Phe-Ala
C)Ile-Lys-His-Tyr
D)Cys-Pro-Lys-Ala

Question 45

You are studying a disease that is caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA.Which of the following molecules are likely to contain the genetic information of the virus?

A)high-energy phosphate groups
B)RNA
C)lipids
D)carbohydrates

Question 46

The length of a particular gene in human DNA, measured from the start site for transcription to the end of the protein-coding region, is 10,000 nucleotides, whereas the length of the mRNA produced from this gene is 4000 nucleotides.What is the most likely reason for this difference?

Question 47

One strand of a section of DNA isolated from the bacterium E.coli reads:
5′-GTAGCCTACCCATAGG-3′
Table 7-29
A.Suppose that an mRNA is transcribed from this DNA using the complementary strand as a template.What will be the sequence of the mRNA in this region (make sure you label the 5′ and 3′ ends of the mRNA)?
B.How many different peptides could potentially be made from this sequence of RNA, assuming that translation initiates upstream of this sequence?
C.What are these peptides? (Give your answer using the one-letter amino acid code.)

Question 48

Figure 7-52 shows an mRNA molecule.
Figure 7-52
Is the mRNA shown prokaryotic or eukaryotic? Explain your answer.

Question 49

Why is the old dogma "one gene-one protein" not always true for eukaryotic genes?

Question 50

Which of the following methods is not used by cells to regulate the amount of a protein in the cell?

A)Genes can be transcribed into mRNA with different efficiencies.
B)Many ribosomes can bind to a single mRNA molecule.
C)Proteins can be tagged with ubiquitin, marking them for degradation.
D)Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.

Question 51

Below is a segment of RNA from the middle of an mRNA.
5′- ...UAGUCUAGGCACUGA ...-3′
Table 7-29
If you were told that this segment of RNA was part of the coding region of an mRNA for a large protein, give the amino acid sequence for the protein that is encoded by this segment of mRNA.Write your answer using the one-letter amino acid code.

Question 52

After treating cells with a mutagen, you isolate two mutants.One carries alanine and the other carries methionine at a site in the protein that normally contains valine.After treating these two mutants again with mutagen, you isolate mutants from each that now carry threonine at the site of the original valine (see Figure 7-67).Assuming that all mutations caused by the mutagen are due to single nucleotide changes, deduce the codons that are used for valine, alanine, methionine, and threonine at the affected site.
Figure 7-67
Table 7-29

Question 53

An extraterrestrial organism (ET) is discovered whose basic cell biology seems pretty much the same as that of terrestrial organisms except that it uses a different genetic code to translate RNA into protein.You set out to break the code by translation experiments using RNAs of known sequence and cell-free extracts of ET cells to supply the necessary protein-synthesizing machinery.In experiments using the RNAs below, the following results were obtained when the 20 possible amino acids were added either singly or in different combinations of two or three:
RNA 1: 5′-GCGCGCGCGCGCGCGCGCGCGCGCGCGC-3′
RNA 2: 5′-GCCGCCGCCGCCGCCGCCGCCGCCGCCGCC-3′
Using RNA 1, a polypeptide was produced only if alanine and valine were added to the reaction mixture.Using RNA 2, a polypeptide was produced only if leucine and serine and cysteine were added to the reaction mixture.Assuming that protein synthesis can start anywhere on the template, that the ET genetic code is nonoverlapping and linear, and that each codon is the same length (like the terrestrial triplet code), how many nucleotides does an ET codon contain?

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

Question 54

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; use each word or phrase only once.
A medium protein
central P RNA
DNA peptidyl transferase small
E polymerase T
large proteasome ubiquitin
Once an mRNA is produced, its message can be decoded on ribosomes.The ribosome is composed of two subunits: the __________ subunit, which catalyzes the formation of the peptide bonds that link the amino acids together into a polypeptide chain, and the __________ subunit, which matches the tRNAs to the codons of the mRNA.During the chain elongation process of translating an mRNA into protein, the growing polypeptide chain attached to a tRNA is bound to the __________ site of the ribosome.An incoming aminoacyl-tRNA carrying the next amino acid in the chain will bind to the __________ site by forming base pairs with the exposed codon in the mRNA.The __________ enzyme catalyzes the formation of a new peptide bond between the growing polypeptide chain and the newly arriving amino acid.The end of a protein-coding message is signaled by the presence of a stop codon, which binds the __________ called release factor.Eventually, most proteins will be degraded by a large complex of proteolytic enzymes called the __________.

Question 55

According to current thinking, the minimum requirement for life to have originated on Earth was the formation of a

A)molecule that could provide a template for the production of a complementary molecule.
B)double-stranded DNA helix.
C)molecule that could direct protein synthesis.
D)molecule that could catalyze its own replication.

Question 56

The following RNA sequence includes the beginning of a sequence coding for a protein.What would be the result of a mutation that changed the C that is bolded and marked by an asterisk to an A?
5′-AGGCUAUGAAUCGACACUGCGAGCCC ...
Table 7-29

Question 57

You have discovered an alien life-form that surprisingly uses DNA as its genetic material, makes RNA from DNA, and reads the information from RNA to make protein using ribosomes and tRNAs, which read triplet codons.Because it is your job to decipher the genetic code for this alien, you synthesize some artificial RNA molecules and examine the protein products produced from these RNA molecules in a cell-free translation system using purified alien tRNAs and ribosomes.You obtain the results shown in Table 7-48. $\begin{array}{c|c}\text { Message } & \text { Peptides produced } \\\hline \text { poly UA } & \text {... Tyr-Cys-Tyr-Cys ... } \\\hline \text { poly UC } & \text {... Phe-Lys-Phe-Lys .... }\\\text { poly UAC } & \ldots \text { lle-lle-lle-lle ... } \\& +\\&\text {... Ser-Ser-Ser-Ser... } \\&+ \\&\text {... Pro-Pro-Pro-Pro ... }\\\hline\text { poly UCA } & \text {... Ala-Ala-Ala-Ala ... } \\& +\\&\text { ... His-His-His-His...}\\&+\\&\text { ... Val-Val-Val-Val...}\\\hline\text { poly AUA } & \ldots \text { Arg-Arg-Arg-Arg ... } \\& +\\&\text { ... Glu-Glu-Glu-Glu... }\\&+\\&\text { ... Tyr-Tyr-Tyr-Tyr ... }\end{array}$ Table 7-48
From this information, which of the following peptides can be produced from poly UAUC?

A)Ile-Phe-Val-Tyr
B)Tyr-Ser-Phe-Ala
C)Ile-Lys-His-Tyr
D)Cys-Pro-Lys-Ala

Question 58

Which of the following molecules is thought to have arisen first during evolution?

A)protein
B)DNA
C)RNA
D)All came to be at the same time.

Question 59

Is the following statement TRUE or FALSE? Explain your answer.
Since introns do not contain protein-coding information, they do not have to be removed precisely from the primary transcript during RNA splicing.In other words, leaving in an extra nucleotide or two should not make a difference to the protein produced.

Question 60

Which of the following statements about the proteasome is FALSE?

A)Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome.
B)Proteases reside in the central cylinder of a proteasome.
C)Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold.
D)The protein stoppers that surround the central cylinder of the proteasome use the energy from ATP hydrolysis to move proteins into the proteasome inner chamber.

Question 61

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; use each word or phrase only once.
incorporation rRNA translation
mRNA snRNA transmembrane
pRNA transcription tRNA
proteins
For a cell's genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called __________.Various kinds of RNA are produced, each with different functions.__________ molecules code for proteins, __________ molecules act as adaptors for protein synthesis, __________ molecules are integral components of the ribosome, and __________ molecules are important in the splicing of RNA transcripts.

Question 62

Figure 7-75A shows the stage in translation when an incoming aminoacyl-tRNA has bound to the A site on the ribosome.Using the components shown in Figure 7-75A as a guide, show on Figures 7-75B and 7-75C what happens in the next two stages to complete the addition of the new amino acid to the growing polypeptide chain.
Figure 7-75