Deck 13: Gene Expression

Question 1

Garrod first proposed that:

A) metabolic defects were due to the lack of an enzyme.
B) metabolic defects were due to excess enzyme production.
C) metabolic defects were due to chromosomal changes.
D) mutations were heritable.
E) metabolic defects did not occur in humans.

Answer 1

A

Question 2

Uracil forms a complementary pair with ____ in RNA and ____ in DNA.

A) adenine; adenine
B) adenine; thymine
C) thymine; thymine
D) thymine; adenine
E) uracil; uracil

Answer 2

A

Question 3

Which of the following is a characteristic of uracil?

A) It has the ability to bond with adenine.
B) It has the ability to bond with guanine.
C) It is a purine.
D) It has the ability to bond with cytosine.
E) It contains two nitrogenous rings.

Answer 3

A

Question 4

How is the four-letter language of nucleic acids converted into the twenty-word language of amino acids?

A) The four nucleic acid bases combine in two-letter combinations that define different amino acids.
B) The four nucleic acid bases combine in three-letter sequences that define different amino acids.
C) Triplets of the two-letter nucleic acid bases are translated into the twenty different amino acids.
D) The four bases each specify one amino acid, which in combination give rise to the remaining sixteen amino acids.
E) The four bases are first converted into tRNA molecules, which can each attach to five amino acids.

Question 5

In the Beadle and Tatum study, it was important that Neurospora was haploid because:

A) it is easier to grow haploid molds in the laboratory.
B) haploid molds have simpler nutritional requirements than do diploid molds.
C) a mutation that arises is not masked by a normal allele on a homologous chromosome.
D) haploid Neurospora will always mutate.
E) diploid Neurospora will always mutate.

Question 6

The total number of different three-base combinations of the four nucleic acid bases is:

A) 12.
B) 16.
C) 20.
D) 64.
E) 256.

Question 7

Figure 13-1 The experimental design in the accompanying figure was used to examine:

A) the relationship between genetic changes and metabolic enzymes.
B) the mutation rate of Neurospora.
C) resistance of Neurospora to genetic poisons.
D) toxicity of arginine metabolites.
E) growth of Neurospora in the presence of different antibiotics.

Question 8

Figure 13-1 What conclusion was associated with mutant strain III in the accompanying figure?

A) It contained all the enzymes needed for normal metabolism.
B) It was missing all the enzymes for metabolism of amino acids.
C) It was missing the enzyme that catalyzes the conversion of citrulline to arginine.
D) It was missing the enzyme that catalyzes the conversion of ornithine to citrulline.
E) It was missing the first enzyme in the arginine metabolic pathway.

Question 9

RNA synthesis is also known as:

A) elongation.
B) reverse transcription.
C) termination.
D) translation.
E) transcription.

Question 10

Figure 13-2 In the accompanying figure, the portion of the molecule containing the anticodon is indicated by the label:

A) 1.
B) 2.
C) 3.
D) 4.
E) 5.

Question 11

Beadle and Tatum began their studies with wild-type Neurospora. How is this organism best characterized?

A) A strain that only grows in the wild
B) A mutant strain that will only grow in the lab on complete medium
C) A strain that will not grow in the lab
D) A virulent strain
E) A normal phenotype that will grow on minimal medium

Question 12

If an mRNA transcript of the human XYZ gene was introduced into a yeast cell, the transcript would be:

A) degraded immediately.
B) translated into a yeast-specific gene.
C) translated into the human XYZ protein.
D) exported outside the cell.
E) transcribed into the XYZ mRNA.

Question 13

Beadle and Tatum irradiated Neurospora and initially grew the mutant strains on complete medium. How were they able to determine the type of mutation for each strain?

A) By growing the mold on a complete medium with extra vitamins and nutrients
B) By growing the mold on minimal media supplemented with different combinations of amino acids and vitamins
C) By growing the mold in its diploid form to see which traits were masked
D) By comparing Neurospora to other species of mold
E) By observing the marked differences in morphology between the different strains

Question 14

What conclusions did Beadle and Tatum reach in their studies of Neurospora ?

A) Each mutant gene affected three enzymes.
B) Each mutant gene affected a pair of enzymes.
C) Each mutant gene affected only one enzyme.
D) Mutant genes had no effect on the enzymes produced by the cells.
E) Each mutant gene affected as many enzymes as were present in a particular metabolic pathway.

Question 15

Which of the following is made from DNA?

A) tRNA only
B) mRNA only
C) rRNA only
D) mRNA and tRNA only
E) mRNA, tRNA, and rRNA

Question 16

Linus Pauling demonstrated that:

A) the structure of hemoglobin was altered by a mutation of a single gene.
B) mutations only caused defects in enzymes.
C) mutations alter the structure of RNA, but not proteins.
D) mutations were inherited.
E) the structure of hemoglobin was altered by mutations in any of a dozen genes.

Question 17

The molecule that connects a growing polypeptide chain and mRNA is called:

A) tRNA.
B) RNA polymerase.
C) rRNA.
D) a promoter.
E) a ribosome.

Question 18

Figure 13-2 Refer to the accompanying figure. The portion of the molecule labeled as 5 is:

A) the attached amino acid.
B) a double-stranded DNA region.
C) a single-stranded DNA region.
D) the anticodon.
E) the codon.

Question 19

Neurospora is an ideal organism to study the effects of genetic mutations because of several reasons. What is one of these?

A) Neurospora is a small mammal.
B) Neurospora grows as a diploid organism.
C) Neurospora requires a medium supplemented with only a few nutrients that it cannot manufacture on its own.
D) Neurospora mutant strains that cannot make a particular amino acid can still grow if that amino acid is added to the growth medium.
E) Neurospora contains homologous chromosomes that are easily viewed with a light microscope.

Question 20

The wobble hypothesis states that:

A) more than one ribosome can bind to an mRNA molecule.
B) some amino acids are coded for by more than one codon.
C) there is more than one stop codon in the genetic code.
D) a particular amino acid may be linked to more than one type of tRNA molecule.
E) certain tRNA anticodons can pair with more than one codon sequence.

Question 21

These noncoding sequences located within coding regions of ____ genes are called ____.

A) only eukaryotic; introns
B) eukaryotic and prokaryotic; introns
C) only prokaryotic; introns
D) only eukaryotic; exons
E) only prokaryotic; exons

Question 22

A "5 ′ cap":

A) prevents translation.
B) prevents the binding of ribosomes.
C) marks the mRNA for degradation.
D) is added to mRNA but not pre-mRNA.
E) protects mRNA from degradation.

Question 23

Introns in pre-mRNA:

A) code for specific protein domains.
B) are spliced out of the message.
C) move within the mRNA, giving rise to new exon combinations.
D) protect pre-mRNA from enzyme degradation.
E) code for important amino acid sequences.

Question 24

The 3 ′ end of eukaryotic pre-mRNAs are changed by:

A) removing the last phosphate group.
B) adding a "cap."
C) copying the last few bases so that it can form a duplex structure.
D) adding 100 − 250 adenine nucleotides.
E) phosphorylation of the mRNA molecule.

Question 25

Why is only one strand of DNA transcribed into mRNA?

A) Because mRNA is only required in small quantities
B) Because transcribing both DNA strands would produce different amino acid sequences
C) Because the other strand would produce the same amino acid sequence in reverse order
D) Because all genes are located on the same DNA strand, while the other strand acts as protection
E) Because the other strand is transcribed directly into amino acids

Question 26

During translocation, the movement of the ribosome repositions the tRNA linked to the growing polypeptide chain to the ____ site, thereby vacating the ____ site for the arrival of a new amino-acyl tRNA.

A) A; P
B) P; A
C) initiation; termination
D) large ribosomal subunit; small ribosomal subunit
E) small ribosomal subunit; large ribosomal subunit

Question 27

How does the first nucleotide at the 5 ′ end of a new mRNA chain differ from the other nucleotides in the chain?

A) The first nucleotide is always a uracil.
B) The first nucleotide is always a cytosine.
C) The first nucleotide retains its triphosphate group, while the others do not.
D) The first nucleotide does not retain its triphosphate group, while the others in the chain do.
E) The first nucleotide is always a modified cytosine.

Question 28

Following peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain, the tRNA in the A site:

A) releases the growing polypeptide chain.
B) picks up another amino acid to add to the chain.
C) moves to the P site of the ribosome.
D) forms a peptide bond with A site of the ribosome.
E) forms a covalent bond with the P site of the ribosome.

Question 29

A polyribosome is:

A) a complex composed of several ribosomes and plus an mRNA transcript.
B) a complex componsed of several ribosomes in eukaryotes.
C) an initiation complex in eukaryotes.
D) an elongation complex in eukaryotes.
E) one ribosome complexed to several mRNAs.

Question 30

Aminoacyl-tRNA synthetases link ____ to their respective tRNA molecules by ____ bonds.

A) amino acids; ionic
B) amino acids; hydrogen
C) amino acids; covalent
D) codons; covalent
E) anticodons; hydrogen

Question 31

RNA is ____ and contains the nitrogenous base ____, which is absent in DNA.

A) single-stranded; thymine
B) double-stranded; uracil
C) single-stranded; uracil
D) double-stranded; thymine
E) single-stranded; cytosine

Question 32

Figure 13-3 Refer to the accompanying figure. The component labeled as B is:

A) DNase.
B) DNA polymerase.
C) RNA primase.
D) RNA polymerase.
E) reverse transcriptase.

Question 33

Figure 13-3 Refer to the accompanying figure. Which label indicates the location of the promoter region?

A) A
B) B
C) C
D) D
E) E

Question 34

During protein synthesis, ribosomes:

A) attach to the mRNA molecule and travel along its length to produce a polypeptide.
B) attach to the DNA molecule and travel along its length to produce an mRNA molecule.
C) translate mRNA into tRNA.
D) transcribe DNA into mRNA.
E) translate tRNA into protein.

Question 35

Figure 13-3 The process illustrated in the accompanying figure is:

A) DNA synthesis.
B) translation.
C) transcription.
D) a frame shift mutation.
E) protein synthesis.

Question 36

A sequence of bases located upstream from a reference point occurs towards the:

A) 3 ′ end of the amino acid sequence.
B) 5 ′ end of the mRNA sequence.
C) 3 ′ end of the mRNA sequence.
D) 5 ′ end of the transcribed DNA strand.
E) carboxyl end of the amino acid sequence.

Question 37

Peptidyl transferase, a _____ molecule, catalyzes the formation of _____ between amino acids at the P and A sites.

A) protein; peptide bonds
B) protein; hydrogen bonds
C) ribozyme; peptide bonds
D) ribozyme; hydrogen bonds
E) protein; templates

Question 38

Leader sequences contain signals that:

A) prevent enzymes from degrading the newly synthesized mRNA.
B) inhibit ribosome binding until the appropriate time.
C) initiate chain termination.
D) allow the ribosomes to be properly positioned for translation of mRNA molecules.
E) allow tRNA molecules to successfully bind to mRNA.

Question 39

Initiation of transcription requires:

A) a promoter sequence.
B) DNA polymerase.
C) an RNA primer.
D) a DNA primer.
E) Okazaki fragments.

Question 40

Ribose differs from deoxyribose by having:

A) two attached nitrogenous bases.
B) one less oxygen.
C) an extra hydroxyl group.
D) an extra carbon in the ring.
E) one less carbon in the ring.

Question 41

Compare and contrast DNA and RNA. Include the similarities and differences in their chemical composition and structure, as well as their general roles within the cell.

Question 42

tRNA molecules are able to act as adapters between amino acids and mRNA during translation because:

A) tRNA binds to ribosomes.
B) tRNA can bind to both mRNA and an amino acid.
C) tRNA anticodons bind to amino acids.
D) tRNA is recognized by RNA polymerase.
E) tRNA molecules bind to promoter sequences to initiate transcription.

Question 43

The template DNA strand is described as being parallel to the complementary RNA strand.
__________________

Question 44

Retroviruses, such as RNA tumor viruses, use __________ to make DNA from their RNA genomes.

A) DNA polymerase
B) DNA-dependent RNA polymerase
C) RNA polymerase
D) primase
E) reverse transcriptase

Question 45

A ____ mutation results in the conversion of a codon specifying an amino acid to a termination codon.

A) nonsense
B) frameshift
C) chromosomal
D) missense
E) silent

Question 46

What is the modern definition of a gene?

A) A DNA sequence that encodes a specific RNA or protein product
B) A DNA sequence that encodes a specific polypeptide
C) An RNA sequence that encodes a single polypeptide
D) A DNA sequence that encodes several proteins
E) A DNA sequence that encodes specific amino acids

Question 47

Proteins synthesized in bacteria have which of the following at their amino terminal end?

A) N-formyl-methionine
B) N-acetyl-adenine
C) adenine triphosphate
D) The AUG codon
E) The UUU codon

Question 48

Translation is initiated at the ____.

A) AUG codon
B) UAG codon
C) anticodon
D) promoter
E) downstream sequence

Question 49

Which of the following numbered events represents the correct sequence of events of prokaryotic translation initiation?
1) large ribosomal subunit binds to initiation complex
2) initiation tRNA binds small ribosomal subunit
3) initiation complex binds to ribosome recognition sequence on mRNA

A) 1 → 2 → 3
B) 1 → 3 → 2
C) 2 → 1 → 3
D) 2 → 3 → 1
E) 3 → 2 → 1

Question 50

The process in which RNA is synthesized using a DNA template is called translation .
__________________

Question 51

The notion that the genetic code is universal suggests a common ancestor for all living organisms.

Question 52

A mutation that replaces one amino acid in a protein with another is called a ____ mutation.

A) frameshift
B) recombinant
C) nonsense
D) missense
E) neutral

Question 53

Mobile genetic elements, such as transposons and retrotransposons, are significant because:

A) the entire human genome is composed of transposons.
B) they are present in the human genome, but not in the genomes of other organisms.
C) mutations caused by retrotransposons contribute greatly to a species' evolution.
D) transposons are the only mechanisms of genetic diversity.
E) only corn contain transposons.

Question 54

A grouping of three nucleotides code for one amino acid.
__________________

Question 55

Binding of the appropriate aminoacyl-tRNA to the A site requires:

A) no energy input.
B) energy supplied by two ATP molecules.
C) energy supplied by GTP.
D) activation of the A site.
E) phosphorylation of the tRNA molecule.

Question 56

List the main steps involved in converting pre-mRNA to mRNA. Explain the purpose of each step.

Question 57

One of the mRNA codons specifying the amino acid leucine is 5 ′ -CUA-3 ′ . Its corresponding anticodon is:

A) 5 ′ -GAT-3 ′ .
B) 3 ′ -AUC-5 ′ .
C) 3 ′ -GAU-5 ′ .
D) 3 ′ -GAT-5 ′ .
E) 5 ′ -GAU-3 ′ .

Question 58

Linus Pauling proposed the one gene - one enzyme hypothesis.

Question 59

Draw a general overview of the flow of genetic information from DNA to protein in eukaryote vs. prokarytotes. You should construct one drawing for eukaryotes and one for prokaryotes. Label all structures, molecules, processes, and cellular compartments.

Question 60

Frameshift mutations result from the:

A) substitution of one base pair for another.
B) substitution of more than one base pair.
C) insertion or deletion of one or two base pairs.
D) substitution of a stop codon for an amino acid-specifying codon.
E) substitution of a start codon for an amino acid codon.

Question 61

Eukaryotic mRNA has a significantly longer half life than its prokaryotic counterpart. How is this accomplished in eukaryotes? What processes tend to degrade mRNA molecules in both eukaryotes and prokaryotes, and why are these processes needed?

Question 62

A(n) nonsense mutation is a base-pair substitution that results in the replacement of one amino acid with another.
__________________

Question 63

Discuss which type of DNA mutation in the coding region of an essential human gene (for example, insulin) would be the most harmful to a phenotype. Consider missense, nonsense, frameshifts, and transposons.

Question 64

Molecular chaperones assist in the folding of newly synthesized mRNAs .
__________________

Question 65

Reverse transcriptase catalyzes the synthesis of DNA from an RNA template.
__________________

Question 66

In eukaryotes, the initiator tRNA carries the amino acid leucine .
__________________

Question 67

In the process of transcription, incoming RNA nucleotides are in their triphosphates form.
__________________

Question 68

The enzyme peptidyl transferase catalyzes peptide bond formation during the elongation stage of translation.
__________________

Question 69

RNA interference i s a process by which noncoding RNA molecules regulate gene expression.

Question 70

The poly-A tail is thought to facilitate the export of mRNA from the nucleus.
__________________

Question 71

One function of sno-RNAs is to process pre-rRNA molecules in the mitochondrion .
__________________

Question 72

Signal-recognition particle RNA is involved in directing the ribosome-mRNA-polypeptide complex to the rough ER .
__________________

Question 73

snRNPs function to splice introns together.
__________________

Question 74

A ribosome has one binding site for mRNA and two binding sites for tRNAs.
__________________

Question 76

Transcription and translation occur simultaneously in prokaryotes. Why can't this process take place in eukaryotes? What disadvantage results from such linking in prokaryotes?

Question 77

What evolutionary role is served by the redundancy of the genetic code?

Question 78

A(n) transposon is a DNA sequence that "jumps" into the middle of a gene.
__________________

Question 79

RNA polymerase binds to the promoter sequence in RNA .
__________________

Question 80

The 3' trailing sequences are located upstream of the stop codon.
__________________