Deck 20: Introduction to Molecular Genetics

Question 1

One strand of the DNA molecule advances in the 3' → 5' direction.In what direction does its complementary strand advance?

A)3' → 5'
B)N-terminal to C-terminal
C)5' → 3'
D)O-terminal to P-terminal
E)There is no set direction for the complementary strand; it depends on the organism.

Answer 1

5' → 3'

Question 2

What important discovery about DNA was made by Irwin Chargaff?

A)The structure of DNA was a double-stranded helix.
B)Chromosomes were DNA-containing structures within the cell.
C)The genetic code consisted of a sequence of 3 bases.
D)DNA replication is a semiconservative process.
E)The amounts of adenine and thymine in all DNA were equal,as were the amounts of guanine and cytosine.

Answer 2

The amounts of adenine and thymine in all DNA were equal,as were the amounts of guanine and cytosine.

Question 3

Hydrogen bonding plays an important role in all but one of the items below.Which one does NOT involve hydrogen bonding?

A)DNA replication
B)DNA double helix
C)DNA primary structure
D)synthesis of mRNA from DNA
E)codon/anticodon recognition

Answer 3

DNA primary structure

Question 4

What is the name for the nucleotide formed from deoxyribose,adenine,and two phosphoryl groups?

A)adenosine phosphate
B)deoxyadenosine phosphate
C)D-adenine diphosphate
D)deoxyriboadenine diphosphate
E)deoxyadenosine diphosphate

Question 5

What sequence on a DNA molecule indicates where RNA polymerase should begin transcription?

A)replication fork
B)Okazaki fragment
C)promoter
D)replication origin
E)anticodon loop

Question 6

What is the function of the enzyme DNA polymerase in replication?

A)It unwinds the double helix of DNA and separates the two strands.
B)It reads the sequence of nucleotides on the parental strand of DNA and catalyzes the polymerization of a complementary daughter DNA strand.
C)It reads the codons on a DNA molecule and catalyzes the polymerization of a complementary mRNA strand.
D)It connects the short Okazaki fragments formed in the lagging strand.
E)It carries the amino acids that are necessary to form a new daughter strand.

Question 7

RNA splicing involves the removal of nucleotide sequences that do not code for a protein in a newly formed mRNA.What are these nonprotein coding sequences called?

A)caps
B)introns
C)exons
D)operons
E)genes

Question 8

The genetic code is said to be "degenerate".What does this term indicate about the genetic code?

A)Different triplet codons serve as code words for the same amino acid.
B)The genetic code contains regions of nonprotein coding sequences.
C)The genetic code can easily undergo mutations that can lead to illnesses such as cancer.
D)The genetic code is repetitive,and is identical in all species.
E)The genetic code must be rewritten several times before a functional protein is formed.

Question 9

Which statement concerning DNA is FALSE?

A)DNA stands for diribonucleic acid.
B)DNA molecules are located in the nucleus of the cell.
C)DNA molecules exist tightly wrapped around proteins called histones.
D)The genetic information of an organism is stored in DNA.
E)The four common bases found in DNA are adenine,cytosine,guanine,and thymine.

Question 10

The mechanism of DNA replication is said to be semi-conservative.Which of the following best describes what this term indicates with respect to DNA replication?

A)The daughter DNA strands are formed by complementary,not identical,base pairing.
B)The daughter DNA strands are formed by both complementary as well as identical base pairing.
C)The daughter DNA strands produced in DNA replication each contain one strand of the original parent DNA and one newly synthesized strand.
D)Nucleoside triphosphates as well as nucleoside monophosphates are used to provide the complementary bases.
E)DNA replication proceeds in both the 3'→5' direction as well as the 5'→3' direction.

Question 11

Which two amino acids are encoded by only a single codon each?

A)proline and glycine
B)cysteine and arginine
C)phenylalanine and isoleucine
D)tyrosine and proline
E)methionine and tryptophan

Question 12

Which nitrogenous base is normally found in RNA,but not in DNA?

A)pyridine
B)urea
C)thymine
D)uracil
E)purine

Question 13

DNA isolated from human cheek cells was found to contain 21% guanine.What else is true about the base composition of this DNA sample?

A)It contains 79% cytosine.
B)It contains 79% adenine and thymine.
C)It contains 21% adenine,21% cytosine,and 21% thymine.
D)It contains 21% cytosine,29% adenine,and 29% thymine.
E)It is impossible to say anything specific about the percentages of adenine,cytosine,and thymine without further analysis.

Question 14

Nucleic acids are polymers of nucleotides.Which of the following correctly represents a nucleotide that may be found in nucleic acids?

A)I
B)II
C)III
D)I,II,and III
E)I and IV

Question 15

What directional flow of information is referred to as the "central dogma of molecular biology"?

A)DNA → RNA → protein
B)RNA → DNA → protein
C)protein → DNA → RNA
D)protein → RNA → DNA
E)RNA → protein → DNA

Question 16

Which of the following statements concerning nucleic acids is FALSE?

A)Nucleic acids are polymers of repeating monomer units called nucleotides.
B)DNA is responsible for the storage of genetic information.
C)RNA is responsible for the transfer and expression of genetic information.
D)A gene is a sequence of bases on a DNA strand that codes for a particular protein.
E)A chromosome is a complex of 46 DNA molecules intertwined with proteins.

Question 17

The genetic code is composed of triplets using four different bases.How many different codons (triplets)are there?

A)12
B)24
C)36
D)64
E)128

Question 18

What term is used to describe the point at which new deoxyribonucleotides are added to the growing daughter strand during DNA replication?

A)replication junction
B)transcription point
C)replication fork
D)parental/daughter boundary
E)addition point

Question 19

The mRNA codon CAU specifies the amino acid histidine (His).What sequence of nucleotides is found in the anticodon loop of the tRNA molecule that carries His to the ribosomes?

A)CAU
B)CAT
C)GTA
D)GUA
E)GUT

Question 20

Who first described the three-dimensional structure of DNA in 1953?

A)Watson and Crick
B)Chargaff
C)Garrow
D)Mendeleev
E)Einstein

Question 21

Approximately how many base pairs make up the human genome?

A)3 million
B)64 million
C)3 billion
D)10 billion
E)It is still unknown.

Question 22

DNA and RNA are polymers of nucleotides.The nucleotides in each of these molecules are joined together by which of the following?

A)complementary base pairing
B)hydrogen bonding
C)β-N-glycosidic linkages
D)3'-5' phosphodiester bonds
E)peptide bonds

Question 23

DNA is a double-stranded nucleic acid that exists as a double helix.Which of the following is responsible for holding the double helix of DNA together?

A)Phosphodiester bonds between the two strands.
B)N-glycosidic linkages between the sugar-phosphate backbone on each strand.
C)Hydrogen bonding between complementary base pairs on the two strands.
D)Disulfide bonds between the nucleotides on the two strands.
E)Thymine dimers between the two strands.

Question 24

Which pyrimidine bases are found in DNA?

A)adenine and thymine
B)thymine and guanine
C)adenine and guanine
D)cytosine and thymine
E)cytosine and adenine

Question 25

What enzyme functions to catalyze the formation of phosphodiester bonds between two fragments of DNA?

A)Thermus aquaticus
B)DNA phosphatase
C)DNA ligase
D)Restriction enzymes
E)Taq polymerase

Question 26

Which of the following is NOT a product of recombinant DNA technology that is used in medicine?

A)insulin
B)aspirin
C)human growth hormone
D)influenza vaccine
E)hepatitis B vaccine

Question 27

Where does protein synthesis occur inside the cell?

A)in the cell membrane
B)at the ribosomes
C)inside the mitochondria
D)at the lysosomes
E)in the nucleus

Question 28

What type of mutation results in the loss of one or more nucleotides from a DNA sequence?

A)omission
B)deletion
C)point
D)silent
E)fragmental

Question 29

What type of mutation involves the substitution of a single base for another in a codon?

A)switch
B)insertion
C)point
D)silent
E)fragmental

Question 30

Which structure correctly represents the dinucleotide sequence GC that is found in DNA?

A)

B)

C)

D)

Question 31

What commonly results when DNA is damaged by ultraviolet light?

A)cysteine dimers
B)pyrimidine dimers
C)the conversion of purine bases to pyrimidine bases
D)the conversion of pyrimidine bases to purine bases
E)an increased production of DNA

Question 32

What is accomplished by the use of gel electrophoresis in DNA analysis?

A)separation of DNA fragments according to size
B)hybridization of DNA fragments
C)formation of daughter DNA molecules
D)identification of base composition
E)rapid DNA synthesis

Question 33

What molecule carries the anticodon sequence that is complementary to the codon sequence on messenger RNA?

A)operons
B)restriction enzymes
C)transfer RNA
D)DNA polymerase
E)ribosomal RNA

Question 34

What is the requirement for a radiolabeled DNA or RNA molecule (i.e.,a probe)to hybridize to a section of DNA?

A)Both strands must contain a primer.
B)A cloning vector must be present.
C)The strands must have the same bacterial origin.
D)The strands must have complementary sequences.
E)The strands must have identical sequences.

Question 35

What is the term used to describe a mutation that does not alter the amino acid sequence of the protein encoded by a gene?

A)nonsense
B)sensible
C)point
D)silent
E)fragmental

Question 36

What is the key function of a DNA primer in the polymerase chain reaction (PCR)?

A)It hybridizes to the beginning of a gene,creating a site for DNA polymerase to initiate DNA synthesis of the selected gene.
B)It aids in winding the newly produced DNA molecule with proteins to form a chromosome.
C)It catalyzes the separation of the two strands of DNA being copied.
D)It is the source of the four nucleotides needed in PCR.
E)It acts as a buffer to main a constant pH in the PCR solution.

Question 37

Which technique allows scientists to produce unlimited amounts of any gene of interest?

A)gel electrophoresis
B)polymerase chain reaction
C)southern blot hybridization
D)thermo coupling
E)the Ames test

Question 38

What term is used to describe bacterial enzymes that are used to "cut" the sugar-phosphate backbone of DNA molecules at specific nucleotide sequences?

A)DNA polymerases
B)DNA phosphatases
C)restriction enzymes
D)retroviral enzymes
E)reverse transcriptases

Question 39

Which of the following is NOT a base common to both DNA and RNA?

A)adenine
B)thymine
C)guanine
D)cytosine
E)All of the choices are bases common to both DNA and RNA.

Question 40

What key role does the bacterium Thermus aquaticus play in the polymerase chain reaction (PCR)?

A)It is the source of the four nucleotides needed in PCR.
B)It serves as the platform on which PCR proceeds.
C)It provides the heat-stable DNA polymerase used in PCR.
D)It aids in winding the newly produced DNA molecule with proteins to form a chromosome.
E)It acts as a buffer to maintain a constant pH in the PCR solution.

Question 41

Base pairing between guanine and cytosine is more stable than base pairing between adenine and thymine.Which of the following best explains why?

A)G/C base pairing involves two large purine bases,while A/T base pairing involves two smaller pyrimidine bases.
B)G/C base pairing involves three hydrogen bonds,while A/T base pairing involves only two hydrogen bonds.
C)G/C base pairs are smaller and more compact than A/T base pairs.
D)G/C base pairs are more widely separated and not as crowded as A/T base pairs.
E)G/C base pairs appear in DNA and RNA,while A/T base pairs appear only in DNA.

Question 42

Which of the following best describes the primary function of mRNA in a cell?

A)to serve as an enzyme in the formation of the DNA double helix
B)to serve as an enzyme in DNA replication
C)to transport amino acids to the ribosomes for protein synthesis
D)to transcribe the instructions for protein synthesis from DNA and carry this information to the ribosomes
E)to serve as the structural site for protein synthesis

Question 43

What enzyme is responsible for reading a parental strand of DNA and catalyzing the polymerization of a complementary daughter strand?

A)peptide polymers
B)DNA isomerase III
C)DNA polymerase
D)transferase coenzyme A
E)None of the choices are correct.

Question 44

Which enzyme catalyzes the transcription of DNA?

A)transfer RNA
B)messenger RNA
C)DNA ligase
D)RNA polymerase
E)DNA polymerase

Question 45

Which of the following correctly describes a triplet codon?

A)An RNA molecule that contains three ribonucleotides.
B)A sequence of three amino acids in a protein that signals for transcription.
C)A sequence of three nucleotides on mRNA that codes for a specific amino acid.
D)A sequence of three reactions that leads to protein synthesis.
E)A DNA molecule that contains three genes that each code for a different protein.

Question 46

Which of the following is a structural and functional component of the ribosome?

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

Question 47

Which of the following represents the backbone structure of a DNA polymer?

A)base-sugar (ribose)
B)phosphate-sugar (deoxyribose)
C)base-sugar (deoxyribose)
D)phosphate-base
E)phosphate-sugar (ribose)

Question 48

Which type of RNA carries the needed amino acids to the ribosomes for use in protein synthesis?

A)transfer RNA
B)messenger RNA
C)ribosomal RNA
D)RNA polymerase
E)None of the choices are correct.

Question 49

Which of the following molecules carries the genetic information for a protein from DNA to the ribosome?

A)mRNA
B)tRNA
C)amino acids
D)coenzyme A
E)ATP

Question 50

Adenine present in one strand of a DNA molecule is always hydrogen bonded to what base in the other strand?

A)thymine
B)guanine
C)cytosine
D)uracil
E)adenine

Question 51

How many turns of the DNA double helix correspond to twenty base pairs?

A)one
B)six
C)ten
D)two
E)twenty

Question 52

Which term represents the process in which the genetic information stored in DNA is read and copied into an mRNA molecule?

A)replication
B)translation
C)transcription
D)cloning
E)mutation

Question 53

Which term describes the process by which a single strand of DNA serves as a template for the synthesis of an RNA molecule?

A)translation
B)transcription
C)initiation
D)elongation
E)replication

Question 54

Meselson and Stahl (1958)reported experimental results involving nitrogen-labeling relevant to which of the following?

A)the helical structure of DNA
B)the role of RNA in DNA transcription
C)the basis for DNA fingerprinting
D)the mechanism of the polymerase chain reaction
E)the semiconservative mechanism of DNA replication

Question 55

Which term refers to the sequence of three nucleotides at the base of the cloverleaf of a tRNA molecule?

A)codon
B)promoter
C)P-site
D)anticodon
E)A-site

Question 56

Which of the following components is bonded to the backbone chain of DNA by N-glycosidic bonds?

A)phosphoryl groups
B)nucleotides
C)pentoses
D)nitrogenous bases
E)ammonia

Question 57

What is the term used to describe the relationship between the nucleotide sequences on the two strands of DNA?

A)They are enantiomers.
B)They are cooperative.
C)They are complementary.
D)They are mirror images.
E)They are identical.

Question 58

Phosphate groups can be esterified at any hydroxyl group on a pentose nucleotide.What position is the most common?

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

Question 59

Which term describes the process by which a message from DNA in the form of mRNA is converted into the primary sequence of amino acids in a protein?

A)translation
B)transcription
C)initiation
D)elongation
E)translocation

Question 60

Which of the following correctly describes a chromosome?

A)The location inside the cell where protein synthesis occurs.
B)A segment of a DNA molecule that codes for a specific protein.
C)A complex of 46 DNA molecules wrapped tightly together in a bundle.
D)A sequence of three nucleotides that code for a specific amino acid.
E)A complex of proteins and a single DNA molecule wrapped tightly together in a bundle.

Question 61

E.coli contains a single circular piece of DNA as its genetic material.

Question 62

Point mutations always result in a change in the amino acid sequence of the protein encoded by the gene.

Question 63

Which of the following are correct base pairs in DNA? 1.adenine and thymine
2.adenine and cytosine
3.thymine and guanine
4.cytosine and guanine

A)1 and 4
B)2 and 3
C)1,2,and 3
D)1,3,and 4
E)All of the choices are correct.

Question 64

Which statement properly describes the difference between ribose and deoxyribose?

A)Ribose is an L-sugar and deoxyribose is a D-sugar.
B)Deoxyribose has one less oxygen atom than ribose.
C)Ribose has an α-arrangement and deoxyribose has a β-arrangement.
D)Ribose is a five-carbon sugar and deoxyribose is a six-carbon sugar.
E)Deoxyribose has two more hydroxyl groups than ribose.

Question 65

Which of the following changes in a DNA molecule may have no effect on the protein for which the DNA codes?

A)a deletion mutation
B)formation of a thymine dimer
C)changing the first base in a triplet
D)changing the second base in a triplet
E)changing the third base in a triplet

Question 66

What type of bond connects the phosphate group to the sugar in a nucleotide?

A)phosphoester bond
B)phosphoether bond
C)glycosidic bond
D)hydrogen bond
E)ionic bond

Question 67

Which of the statements concerning the nucleotide with the name adenosine-5'-monophosphate (AMP)is FALSE?

A)It is a ribonucleotide.
B)It is composed of ribose,adenine,and a single phosphate group.
C)It is found in RNA only.
D)The phosphate group is attached to the 5' carbon of adenine.
E)All of the statements are true.

Question 68

A DNA template strand having the sequence shown below would produce an mRNA molecule with what sequence? 3'-CGATCA-5'

A)3'-CGATCA-5'
B)3'-CGAUCA-5'
C)5'-CGAUCA-3'
D)5'-GCUAGU-3'
E)5'-GCTAGT-3'

Question 69

What is the term used to describe complexes of many ribosomes all simultaneously translating a single mRNA?

A)carcinogens
B)promoters
C)polysomes
D)codons
E)mutagens

Question 70

A DNA strand has the partial sequence 5'-GACTGA-3'.What would be the sequence of its complementary strand?

A)5'-AGUCAG-3'
B)3'-AGTCAG-5'
C)5'-CTGACT-3'
D)3'-CTGACT-5'
E)5'-CUGACU-3'

Question 71

Which of the following is NOT a component of a nucleotide?

A)nitrogenous base
B)five-carbon sugar
C)phosphoryl group
D)amino acid
E)A nucleotide consists of all of these components.

Question 72

The peptidyl tRNA binding site holds a tRNA molecule bonded to the growing peptide chain.

Question 73

Which statement concerning the double helix structure of DNA is FALSE?

A)The helix completes one turn every 10 base pairs.
B)Base pairs in the double helix are attached by way of hydrogen bonding.
C)The two strands of the double helix are called parallel strands.
D)The base pairs are directed in toward the middle of the double helix.
E)In the double helix,adenine connects to thymine and cytosine connects to guanine.

Question 74

All tRNA molecules have a CCA sequence at their 3' ends.

Question 75

In eukaryotes,the initiator tRNA is bonded to methionine.

Question 76

A gene contains the sequence 3'-GACTGA-5' on its template strand.What would be the sequence of the transcribed mRNA molecule?

A)3'-GACUGA-5'
B)5'-GACUGA-3'
C)5'-CTGACT-3'
D)5'-CUGACU-3'
E)3'-AGTCAG-5'

Question 77

Which statement is FALSE concerning the RNA structure?

A)RNA is usually single-stranded.
B)RNA contains ribose instead of deoxyribose.
C)RNA has a phosphoester linkage connecting the sugar to the phosphate group.
D)Thymine is not in RNA.
E)RNA and DNA are approximately the same size.

Question 78

The two strands of the DNA molecule are antiparallel to one another.

Question 79

Which term is used to describe the process in which a double stranded DNA molecule unwinds,separates,and each strand serves as a template in the synthesis of its complement?

A)cloning
B)replication
C)duplication
D)transcription
E)mutation

Question 80

Transfer RNA (tRNA)is a complementary copy of a gene on DNA.