Chapter 13 -Gene expression

Translocation is the process whereby the __________ moves in order to place the tRNA bound to the growing polypeptide chain in the __________ site, thereby freeing the __________ site for a new aminoacyl-tRNA. a. mRNA; A; P b. ribosome; P; A c. tRNA; P; A d. ribosome; A; P e. tRNA; A;P

b. ribosome; P; A

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

a. N-formyl-methionine

Substitution of one base pair for another can result in a __________ mutation that results in the conversion of an amino acid specifying codon to a termination codon. a. nonsense b. frameshift c. chromosomal d. missense e. silent

a. nonsense

Which of the following serves as an "adapter" in protein synthesis and bridges the gap between mRNA and proteins? a. tRNA b. cDNA c. rRNA d. promoter sequences e. DNA

tRNA

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

d. 2 ® 3 ® 1

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.

d. 64.

Aminoacyl-tRNA synthetases __________ link __________ to their respective tRNA molecules. a. ionically; mRNAs b. loosely; mRNAs c. terminally; codons d. covalently; amino acids e. enzymatically; codons

d. covalently; amino acids

Which of the following is a characteristic of uracil? a. The ability to bond with adenine. b. The ability to bond with guanine. c. It is a purine. d. The ability to bond with cytosine. e. It contains two nitrogenous rings

a. The ability to bond with adenine.

A gene can now be defined as: a. a DNA sequence that carries information to produce a specific RNA or protein product. b. a DNA nucleotide sequence that carries information to produce a specific polypeptide. c. a DNA or RNA sequence that carries information to produce a single polypeptide. d. a DNA nucleotide sequence that carries information to produce an enzyme. e. a DNA or RNA sequence that carries information to produce a specific polypeptide.

a. a DNA sequence that carries information to produce a specific RNA or protein product.

A polyribosome is: a. a complex of many ribosomes and an mRNA. b. a complex of many ribosomes in eukaryotes. c. an initiation complex in eukaryotes. d. an elongation complex in eukaryotes. e. a complex of a ribosome with its two subunits and several mRNAs.

a. a complex of many ribosomes and an mRNA.

Initiation of transcription requires: a. a promoter sequence. b. DNA polymerase. c. an RNA primer. d. a DNA primer. e. Okazaki fragments.

a. a promoter sequence.

Uracil forms a complementary pair with __________ in RNA and __________ in DNA. a. adenine; adenine b. adenine; thymine c. thymine; thymine d. uracil; adenine e. adenine; uraci

a. adenine; adenine

During protein synthesis, ribosomes: a. attach to the mRNA molecule and travel along its length. b. attach to the DNA molecule and travel along its length to produce an mRNA molecule. c. translate mRNA into tRNA. d. transcribe mRNA to tRNA. e. translate mRNA into DN

a. attach to the mRNA molecule and travel along its length.

The codon is found in the: a. mRNA. b. nontemplate strand of DNA. c. template strand of DNA. d. tRNA. e. rRNA.

a. mRNA.

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 inheritable. e. metabolic defects did not occur in humans.

a. metabolic defects were due to the lack of an enzyme.

In essentially all organisms, the AUG codon codes for: a. the initiation of translation. b. the termination of transcription. c. the termination of chain elongation. d. the amino acid valine. e. a termination tRNA molecule

a. the initiation of translation.

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.

a. the structure of hemoglobin was altered by a mutation of a single gene.

Which of the following numbered terms represents the correct order of sequences in a prokaryotic mRNA molecule as it was synthesized? 1) 3¢ trailing sequences 2) coding sequences 3) leader sequences 4) termination signals a. 1 ® 2 ® 3 ® 4 b. 3 ® 2 ® 4 ® 1 c. 2 ® 1 ® 4 ® 3 d. 4 ® 2 ® 1 ® 3 e. 3 ® 4 ® 2 ® 1

b. 3 ® 2 ® 4 ® 1

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

b. Because transcribing both DNA strands would produce different amino acid sequences.

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

b. By growing the mold on minimal media supplemented with different combinations of amino acids, vitamins, etc.

How is the 4-letter language of nucleic acids converted into the 20-word language of amino acids? a. The 4 nucleic acid bases combine in 2-letter combinations that define different amino acids. b. The 4 nucleic acid bases combine in 3-letter sequences that define different amino acids. c. Triplets of the 2-letter nucleic acid bases are translated into the 20 different amino acids. d. The 4 bases each specify 1 amino acid, which give rise to the remaining 16 amino acids. e. The 4 bases are first converted into tRNA molecules, which can each attach to 5 amino acids

b. The 4 nucleic acid bases combine in 3-letter sequences that define different amino acids.

Where is the amino-acid binding site located on the tRNA molecule? a. in the middle of the loop b. at the end of the 3¢ end of the molecule c. in the first loop d. along the longest stretch of base pairing in the molecule e. on the 5¢ end of the molecule

b. at the end of the 3¢ end of the molecule

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

b. recombinant

Walter Gilbert proposed that exons are: a. remnants of older life forms. b. sequences that code for protein domains that are shuffled to form new proteins. c. the result of mutation of introns. d. not present in prokaryotes. e. sequences that interrupt the coding sequences of protein

b. sequences that code for protein domains that are shuffled to form new proteins.

A sequence of bases located upstream from a reference point occurs: a. towards the 3¢ end of the amino acid sequence. b. towards the 5¢ end of the mRNA sequence. c. towards the 3¢ end of the mRNA sequence. d. towards the 5¢ end of the transcribed DNA strand. e. towards the carboxyl end of the amino acid sequence.

b. towards the 5¢ end of the mRNA sequence.

Introns in pre-mRNA are known to: a. code for specific protein domains. b. undergo excision, whereby they are spliced out of the message. c. be able to move within the mRNA, thereby giving rise to new exon combinations. d. protect pre mRNA from enzyme degradation. e. code for important amino acid sequences

b. undergo excision, whereby they are spliced out of the message.

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¢

c. 3¢-GAU-5¢.

Why was it important in the studies of Beadle and Tatum that Neurospora is haploid? a. Because it is easier to grow haploid molds in the laboratory. b. Because haploid molds have simpler nutritional requirements than do diploid molds. c. Because a mutation that arises is not masked by a normal allele on a homologous chromosome. d. Because haploid Neurospora will always mutate. e. Because diploid Neurospora will always mute

c. Because a mutation that arises is not masked by a normal allele on a homologous chromosome.

What conclusions did Beadle and Tatum reach with 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

c. Each mutant gene affected only one enzyme.

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.

c. The first nucleotide retains its triphosphate group, while the others do not.

Ribose differs from deoxyribose by having: a. two attached bases. b. one less oxygen. c. an extra hydroxyl group. d. an extra carbon in the ring. e. one less carbon in the ring

c. an extra hydroxyl group.

Binding of the appropriate aminoacyl-tRNA to the A site requires: a. no additional energy. b. the input of two ATP molecules to supply the needed energy. c. energy supplied by GTP. d. activation of the A site. e. phosphorylation of the tRNA molecule

c. energy supplied by GTP.

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

c. moves to the P site of the ribosome.

Frameshift mutations result from: a. the substitution of one base pair for another. b. the substitution of more than one base pair. c. the insertion or deletion of one or two base pairs. d. the substitution of a stop codon for an amino acid-specifying codon. e. the substitution of a start codon for an amino acid codon.

c. the insertion or deletion of one or two base pairs.

The enzyme peptidyl transferase, which catalyzes the transfer of the polypeptide chain attached to the tRNA in the __________ site to the aminoacyl-tRNA in the __________ site, is thought to be a(n) __________ molecule and not a protein. a. A; P; rDNA b. P; A; tRNA c. A; P; mRNA d. P; A; rRNA e. P; A; sugar

d. P; A; rRNA

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 molecul

d. adding 100-250 adenine nucleotides.

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 to translate the message. e. allow tRNA molecules to successfully bind to mRNA

d. allow the ribosomes to be properly positioned to translate the message.

The translocation process requires: a. no additional energy. b. activation of the P site. c. the input of two ATP molecules to supply the needed energy. d. energy supplied by GTP. e. phosphorylation of the mRNA molecule.

d. energy supplied by GTP.

Interrupted coding sequences include long sequences of bases that do not code for amino acids. These noncoding sequences, called __________, are found in __________ cells. a. exons; only prokaryotic b. introns; only prokaryotic c. exons; only eukaryotic d. introns; only eukaryotic e. exons; both prokaryotic and eukaryotic

d. introns; only eukaryotic

If a human gene mRNA were placed into a cell of yeast, it would be: a. degraded immediately. b. translated into a repeating amino acid chain. c. translated into a chain of random amino acids not resembling the protein in humans. d. translated into the protein that is found in humans. e. integrated into the genome of the yeast

d. translated into the protein that is found in humans.

Which of the following is not a reason why Neurospora is an ideal organism to study the effects of genetic mutations? a. Neurospora is easy to grow. b. Neurospora grows as a haploid organism. c. Neurospora manufactures all its necessary molecules when grown on a minimal medium. d. A mutant Neurospora strain 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

e. Neurospora contains homologous chromosomes that are easily viewed with a light microscope

RNA differs from DNA in all of the following except: a. RNA is usually single-standed. b. RNA lacks thymine. c. RNA contains uracil. d. RNA contains ribose. e. RNA contains cytosine

e. RNA contains cytosine

All of the following characteristics of tRNA molecules are true except:: a. They are recognized by ribosomes. b. They have an anticodon. c. They have an attachment site for an amino acid. d. They are recognized by a specific aminoacyl-tRNA synthetase. e. They are considerably larger than rRNA molecules.

e. They are considerably larger than rRNA molecules.

Beadle and Tatum began their studies with wild-type Neurospora, which is: a. Neurospora 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 of Neurospora. e. a normal phenotype that will grow on minimal medium

e. a normal phenotype that will grow on minimal medium

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.

e. certain tRNA anticodons can pair with more than one codon sequence.

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

e. mRNA, tRNA, and rRNA

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. 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.

e. protects mRNA from degradation.

Retroviruses or RNA tumor viruses use __________ to make DNA. a. DNA polymerase b. DNA-dependent RNA polymerase c. RNA polymerase d. primase e. reverse transcriptase

e. reverse transcriptase

RNA synthesis is also known as: a. elongation. b. reverse transcription. c. termination. d. translation. e. transcription

e. transcription