Chapter 14

Question 1

Normally, Neurospora can synthesize all 20 amino acids. A certain strain of this mold cannot grow in minimal nutritional medium, but grows only when the amino acid leucine is added to the medium. This strain

A. is dependent on leucine for energy.
B. has a mutation affecting a biochemical pathway leading to the synthesis of carbohydrates.
C. has a mutation affecting the biochemical pathways leading to the synthesis of all 20 amino acids.
D. has a mutation affecting the biochemical pathway leading to the synthesis of leucine.
E. has a mutation affecting the biochemical pathways leading to the syntheses of 19 of the 20 amino acids.

Answer 1

D

Question 2

Which statement about RNA is not true?

A. Transfer RNA functions in translation.
B. Ribosomal RNA functions in translation.
C. RNAs are produced by transcription.
D. Messenger RNAs are produced on ribosomes.
E. DNA codes for mRNA, tRNA, and rRNA.

Answer 2

D

Question 3

Which of the following is not a difference between RNA and DNA?

A. RNA has uracil; DNA has thymine.
B. RNA has ribose; DNA has deoxyribose.
C. RNA has five bases; DNA has four.
D. RNA is a single polynucleotide strand; DNA is a double strand.
E. RNA molecules are smaller than human chromosomal DNA molecules.

Answer 3

C

Question 4

An mRNA has the sequence 5′-AUGAAAUCCUAG-3′. What is the template DNA strand for this sequence?

A. 5′-TACTTTAGGATC-3′
B. 5′-ATGAAATCCTAG-3′
C. 5′-GATCCTAAAGTA-3′
D. 5′-TACAAATCCTAG-3′
E. 5′-CTAGGATTTCAT-3′

Answer 4

E

Question 5

The adapters that allow translation of the four-letter nucleic acid language into the 20-letter protein language are called

A. aminoacyl-tRNA synthetases.
B. transfer RNAs.
C. ribosomal RNAs.
D. messenger RNAs.
E. ribosomes.

Answer 5

B

Question 6

Which of the following does not occur after eukaryotic mRNA is transcribed?

A. Binding of RNA polymerase to the promoter
B. Capping of the 5′ end
C. Addition of a poly A tail to the 3′ end
D. Splicing out of the introns
E. Transport to the cytosol

Answer 6

A

Question 7

Transcription

A. produces only mRNA.
B. requires ribosomes.
C. requires tRNAs.
D. produces RNA growing from the 5′ end to the 3′ end.
E. takes place only in eukaryotes.

Answer 7

D

Question 8

Which statement about translation is not true?

A. Translation is RNA-directed polypeptide synthesis.
B. An mRNA molecule can be translated by only one ribosome at a time.
C. The same genetic code operates in almost all organisms and organelles.
D. Any ribosome can be used in the translation of any mRNA.
E. There are both start and stop codons.

Answer 8

B

Question 9

The genetic code

A. is different for prokaryotes and eukaryotes.
B. has changed during the course of recent evolution.
C. has 64 codons that code for amino acids.
D. has more than one codon for many amino acids
E. is ambiguous.

Answer 9

D

Question 10

Which statement about RNA splicing is not true?

A. It removes introns.
B. It is performed by small nuclear ribonucleoprotein particles (snRNPs).
C. It removes the introns at the ribosome.
D. It is usually directed by consensus sequences.
E. It shortens the RNA molecule.

Answer 10

C

Question 11

Which of the following statements about Garrod’s observations is false?

A. Alkaptonuria is a genetic disease.
B. Garrod showed that homogentisic acid accumulated in the blood of people suffering from alkaptonuria.
C. Garrod proposed that homogentisic acid is a breakdown product of tyrosine.
D. Garrod isolated the enzyme homogentisic acid oxidase.
E. Garrod coined the term “inborn errors in metabolism.”

Answer 11

D

Question 12

Beadle and Tatum worked with cultures of the bread mold, Neurospora crassa. Which of the following statements about the work of Beadle and Tatum is false?

A. Prototrophic strains of Neurospora could grow on minimal medium.
B. Each auxotrophic strain had a specific nutritional requirement not displayed by the prototroph.
C. Strains that contained the mutant alleles arose spontaneously.
D. Several different classes of auxotrophs exist for nutrients, such as arginine, that is the product of a biosynthetic pathway.
E. Each of the arginine auxotrophs had a defective allele for one gene coding for one enzyme involved in one step of the arginine biosynthetic pathway.

Answer 12

C

Question 13

RNA and DNA differ in a number of ways. Which one of the following is not a difference between RNA and DNA?

A. RNA is primarily a single-stranded molecule.
B. The nucleotides contain different sugars.
C. Uracil is present in RNA and thymine is present in DNA.
D. Single-stranded RNA can fold into complex shapes whereas DNA does not.
E. RNA is a polynucleotide whereas DNA is not.

Answer 13

E

Question 14

The “central dogma” of molecular biology is sometimes presented diagrammatically (as shown). Which of the following statements about the central dogma is false?

A. The arrow from DNA to RNA represents transcription-DNA-directed RNA synthesis.
B. Information never moves from RNA to DNA.
C. The molecule involved in the flow of information from RNA to protein is transfer RNA.
D. Information never flows from protein to nucleic acids.
E. In eukaryotes, mRNA carries the genetic information from the nucleus to the cytoplasm.

Answer 14

B

Question 15

Which of the following statements about the initiation of transcription (shown) is false?

A. A gene’s promoter is a sequence of DNA to which RNA polymerase binds.
B. Promoters determine the direction in which transcription will proceed.
C. All promoters have the same DNA sequence.
D. The same DNA strand can be a template for one gene, and the complementary strand for another gene.
E. Promoters differ in their RNA polymerase binding effectiveness.

Answer 15

c

Question 16

Which amino acid is coded for by the triplet nucleotide sequence 3′-GTA-5′ on the template DNA strand?

A. Valine
B. Histidine
C. Tyrosine
D. Proline
E. Serine

Answer 16

B

Question 17

Which of the following statements does not describe a property of the genetic code shown?

A. All codons specify different amino acids.
B. The start codon that initiates translation codes for methionine.
C. The genetic code is not ambiguous.
D. Codons are read in the 5′-to-3′ direction in the mRNA sequence.
E. The genetic code is (nearly) universal to all species.

Answer 17

A

Question 18

In the figure shown, A is the _______ region; B is the _______ region; and this gene includes _______ introns and _______ exons.

A. promoter; terminator; 2; 3
B. promoter; terminator; 3; 2
C. terminator; promoter; 2; 3
D. terminator; promoter; 3; 2
E. promoter; stop codon; 2; 3

Answer 18

A

Question 19

Complete the following sentence about the figure shown: The process labeled A is _______; the process labeled B is _______; and if introns were present in the target DNA sequence, loops would result.

A. denaturation; reannealing
B. denaturation; hybridization
C. hybridization; denaturation
D. reannealing; denaturation
E. replication; hybridization

Answer 19

B

Question 20

This figure shows some of the processing steps that transform the RNA primary transcript (pre-mRNA) into mature mRNA. Which of the following is not a difference between pre-mRNA and mature mRNA?

A. The presence of introns
B. The presence of a G cap
C. The presence of poly A tail
D. The presence of promoter and terminator sequences
E. The presence of consensus sequences

Answer 20

D

Question 21

Which of the following statements about transfer RNA (tRNA) is true?

A. Each tRNA anticodon is specific for one codon.
B. The 3′ end of the tRNA molecule varies depending on the amino acid it will bind.
C. Activating enzymes (aminoacyl-tRNA synthetases) link together a specific amino acid with a specific tRNA.
D. A DNA master codon of 3′-TAC-5′ would have an anticodon on a tRNA of 3′-CAU-5′.
E. tRNA binds to mRNA (via its anticodon), but not to tRNA.

Answer 21

C

Question 22

Which of the following statements about the ribosomes shown is false?

A. Ribosomes consist of two subunits, small and large.
B. The P site is where the initial tRNAmet will bind.
C. The A site is the site where binding tRNA between the mRNA codon and tRNA anticodon occurs.
D. The P site is where tRNAs add their amino acids to the growing polypeptide chain.
E. The E site is where the growing polypeptide chain is held while the next tRNA is bound.

Answer 22

E

Question 23

Below is a list of five steps that occur during the initiation of translation. Which of the following would be considered the third step in this process?

A. Large ribosomal subunit binds to mRNA.
B. Anticodon of methionine-tRNA base pairs with its anticodon on mRNA.
C. Small ribosomal subunit binds mRNA.
D. Anticodon of charged tRNA base pairs with the codon at the A site.
E. Peptide linkage forms.

Answer 23

A

Question 24

The figure below shows polypeptide elongation and the genetic code table. What will be the fourth amino acid in the polypeptide?

A. Proline
B. Tyrosine
C. Alanine
D. Arginine
E. Valine

Answer 24

C

Question 25

The following figure shows the movement of a newly formed polypeptide into the ER. Which of the following statements about this process is false?

A. The entire protein is synthesized before the ribosome attaches to the ER.
B. Proteins headed for the ER have an N-terminal signal sequence.
C. mRNA is translated as the newly made protein crosses the ER membrane.
D. A receptor protein in the ER membrane binds the ribosome.
E. The completed polypeptide folds in the lumen of the ER.

Answer 25

A

Question 26

The direction of synthesis for a new mRNA molecule is ___ from a ___ DNA template strand.

A. 5’ to 3’ ; 5’ to 3’
B. 5’ to 3’ ; 3’ to 5’
C. 3’ to 5’ ; 5’ to 3’
D. 3’ to 5’ ; 3’ to 5’
E. 5’ to 5’ ; 3’ to 3’

Answer 26

B

Question 27

The formation of a peptide bond between an amino acid at the P site and an amino acid at the A site during translation is catalyzed by

A. the large ribosomal subunit.
B. the small ribosomal subunit.
C. proteins that are part of the ribosome.
D. the initiation complex.
E. initiation factors.

Answer 27

A

Question 28

The adapters that allow translation of thef our-letter nucleic acid language into the 20-letter protein language are called

A. aminoacyl tRNA synthetases.
B. transfer RNAs.
C. ribosomal RNAs.
D. messenger RNAs.
E. ribosomes.

Answer 28

B

Question 29

Exons are

A. spliced out of the original transcrip.
B. spliced together from the original transcript.
C. spliced to introns to form the final transcript.
D. much larger than introns.
E. larger than the origianl coding region.

Answer 29

B

Question 30

Genes code for

A. enzymes.
B. polypeptides.
C. RNA.
D. All of the above
E. None of the above

Answer 30

D

Question 31

The study of Neurospora mutants grown on various supplemented media led to

A. a determination of the steps in biological pathways.
B. the one-gene, one-enzyme hypothesis.
C. the idea that genes are “on” chromosomes.
D. Both a and b
E. Both a and c

Answer 31

D

Question 32

Fewer different tRNA molecules exist than might have been expected for the complexity of its function. This is possible because

A. the third position of the codon does not have to pair conventionally.
B. the second position of the codon does not have to pair conventionally.
C. the anticodon does not have the conventional bases.
D. there are fewer amino acids than there are possible codons.
E. the code is degenerating.

Answer 32

A

Question 33

In eukaryotes, ribosomes become associated with endoplasmic reticulum membranes when

A. a signal sequence on the mRNA interacts with a receptor protein on the membrane.
B. a signal sequence on the ribosome interacts with a receptor protein on the membrane.
C. a signal sequence at the amino terminus of the protein being synthesized interacts with a receptor protein on the ribosome.
D. a signal sequence ont he protein being synthesized interacts with a signal recognition particle and both bind to the endoplasmic reticulum.
E. the messenger RNA rasses through a pore in the membrane.

Answer 33

D

Question 34

The process of transcription synthesizes

A. transfer RNA.
B. messenger RNA.
C. ribosomal RNA.
D. proteins.
E. a, b, and c

Answer 34

E

Question 35

DNA is composed of two strands, only one of which typically is used as a template for RNA synthesis. By what mechanism is the correct strand chosen?

A. Both strands are tried, and the one that works is remembered.
B. Only one strand has the start codon.
C. The promoter directs the RNA polymerase to the correct strand.
D. A start factor informs the system.
E. It is chosen randomly.

Answer 35

C

Question 36

How does RNA differ from DNA?

A. RNA contains uracil instead of thymine and it is usually single-stranded.
B. RNA contains uracil instead of thymine and it is usually double-stranded.
C. RNA contains thymine instead of cytosine and it is usually single-stranded.
D. RNA contains a 6-carbon (hexose) sugar instead of a 5-carbon (pentose) sugar.
E. DNA is always in the nucleus and RNA is always in the cytoplasm (in eukaryotic cells).

Answer 36

A

Question 37

The guanosine triphosphate (GTP) cap that is added to the 5’ end of primary mRNA

A. is part of the first codon and is translated.
B. provides the mRNA molecule with a poly A tail.
C. facilitates the binding of mRNA to ribosomes.
D. forms hydrogen bonds with the tRNA.
E. helps transfer amino acids to the ribosomes.

Answer 37

C