Deck 13: Gene Expression

Question 1

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.

Answer 1

A

Question 2

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

Answer 2

B

Question 3

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

Answer 3

C

Question 4

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 5

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) an 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 6

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.

Question 7

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 8

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 9

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

Question 10

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 11

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 12

How is the four-letter language of nucleic acids converted into the 20-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 20 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 13

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 14

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 15

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.

Question 16

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 17

RNA synthesis is also known as:

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

Question 18

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 19

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 20

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 21

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 22

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 23

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 24

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 25

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 26

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 27

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 28

A sequence of bases located upstream from a reference point occurs toward 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 29

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 30

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 31

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 32

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 33

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 34

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 35

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 36

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 37

The 3′ end of eukaryotic pre-mRNAs is 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 38

Initiation of transcription requires:

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

Question 39

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 40

A polyribosome is:

A) a complex composed of several ribosomes and plus an mRNA transcript
B) a complex composed 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 41

Translation is initiated at the ____.

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

Question 42

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 43

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 44

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 45

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

Question 46

Draw an overview of the flow of genetic information from DNA to protein in eukaryote and prokaryotes. Construct one drawing for eukaryotes and one for prokaryotes. Label all structures, molecules, processes, and cellular compartments.

Question 47

A grouping of three nucleotides codes for one amino acid.

Question 48

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 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

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 51

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 52

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

Question 53

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

Question 54

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 55

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 56

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 57

List the differences in prokaryotic and eukaryotic mRNAs and explain the purpose of these differences.

Question 58

Compare DNA and RNA. Be sure to include differences in their chemical composition and structure and their roles within the cell.

Question 59

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 60

Linus Pauling proposed the one gene - one enzyme hypothesis.

Question 61

Molecular chaperones assist in the folding of newly synthesized mRNAs.

Question 62

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

Question 63

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

Question 64

RNA polymerase binds to the promoter sequence in RNA.

Question 65

How does the redundancy of the genetic code contribute to evolution?

Question 66

One function of snoRNAs is to process pre-rRNA molecules in the mitochondrion.

Question 67

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

Question 69

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

Question 70

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

Question 71

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

Question 72

snRNPs function to splice introns together.

Question 73

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

Question 74

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

Question 75

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 76

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

Question 77

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

Question 78

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 79

A single nucleotide substitution within a gene is associated with type 1 diabetes and a decrease in insulin secretion. What type of mutation is this? What type of protein (ion channel, hormone, peptide/hormone channel, peptide/hormone pump) is affected?

Question 80

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