Bio 112 Final exam chapters 15-18

Question 1

Refer to the treatments listed below to answer the following question.
You isolate an infectious substance capable of causing disease in plants, but you do not
know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four
methods at your disposal to analyze the substance and determine the nature of the
infectious agent.
I. Treat the substance with enzymes that destroy all nucleic acids and then determine
whether the substance is still infectious.
II. Filter the substance to remove all elements smaller than what can be easily seen
under a light microscope.
III. Culture the substance on nutritive medium, away from any plant cells.
IV. Treat the sample with proteases that digest all proteins and then determining
whether the substance is still infectious.
If you already know that the infectious agent was either bacterial or viral, which
method(s) listed above would allow you to distinguish between these two possibilities?
A) I
B) II
C) II or III
D) IV
E) either II or IV

Answer 1

C) II or III

Question 2

Use the following information to answer the question below.
The herpes viruses are important enveloped DNA viruses that cause disease in vertebrates and in some invertebrates such as oysters. Some of the human forms are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can later reactivate, replicate again, and infect others. In electron micrographs of HSV infection, it can be seen that the intact virus initially reacts with cell surface proteoglycans, then with specific receptors. This is later followed by viral capsids docking with nuclear pores. Afterward, the capsids go from being full to being “empty.” Which of the following best fits these observations?
A) Viral capsids are needed for the cell to become infected; only the capsids enter the
nucleus.
B) The viral envelope is not required for infectivity, since the envelope does not enter
the nucleus.
C) Only the genetic material of the virus is involved in the cell’s infectivity and is injected
like the genome of a phage.
D) The viral envelope mediates entry into the cell, the capsid mediates entry into the nuclear membrane, and the genome is all that enters the nucleus.
E) The viral capsid mediates entry into the cell, and only the genomic DNA enters the
nucleus, where it may or may not replicate.

Answer 2

D) The viral envelope mediates entry into the cell, the capsid mediates entry into the nuclear membrane, and the genome is all that enters the nucleus

Question 3

Which of the following characteristics, structures, or processes is common to bacteria
and viruses?
A) metabolism
B) ribosomes
C) genetic material composed of nucleic acid
D) cell division
E) independent existence

Answer 3

C) genetic material composed of nucleic acid

Question 4

A bacterium is infected with an experimentally constructed bacteriophage composed
of the T2 phage protein coat and T4 phage DNA. The new phages produced would
have ________.
A) T2 protein and T4 DNA
B) T2 protein and T2 DNA
C) T4 protein and T4 DNA
D) T4 protein and T2 DNA

Answer 4

C) T4 protein and T4 DNA

Question 5

Viruses ________.
A) manufacture their own ATP, proteins, and nucleic acids
B) use the host cell to copy themselves and make viral proteins
C) use the host cell to copy themselves and then synthesize their own proteins
D) metabolize food and produce their own ATP

Answer 5

B) use the host cell to copy themselves and make viral proteins

Question 6

In trying to determine whether DNA or protein is the genetic material, Hershey and
Chase made use of which of the following facts?
A) DNA contains sulfur, whereas protein does not.
B) DNA contains phosphorus, whereas protein does not.
C) DNA contains nitrogen, whereas protein does not.
D) DNA contains purines, whereas protein includes pyrimidines.
E) RNA includes ribose, whereas DNA includes deoxyribose sugars.

Answer 6

B) DNA contains phosphorus, whereas protein does not.

Question 7

7) In an analysis of the nucleotide composition of DNA, which of the following will be
found?
A) A = C
B) A = G and C = T
C) A + C = G + T
D) G + C = T + A

Answer 7

C). A + C = G + T

Question 8

For a science fair project, two students decided to repeat the Hershey and Chase
experiment, with modifications. They decided to label the nitrogen of the DNA, rather
than the phosphate. They reasoned that each nucleotide has only one phosphate and
two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than
labeling the phosphates. Why won’t this experiment work?
A) There is no radioactive isotope of nitrogen.
B) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too
dangerous for too long.
C) Although there are more nitrogens in a nucleotide, labeled phosphates actually have
16 extra neutrons; therefore, they are more radioactive.
D) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity
would not distinguish between DNA and proteins.

Answer 8

D) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity
would not distinguish between DNA and proteins.

Question 9

In analyzing the number of different bases in a DNA sample, which result would be
consistent with the base-pairing rules?
A) A = G
B) A + G = C + T
C) A + T = G + T
D) A = C
E) G = T

Answer 9

B) A + G = C + T

Question 10

Of the following, which is the most current description of a gene?
A) a unit of heredity that causes formation of a phenotypic characteristic
B) a DNA subunit that codes for a single complete protein
C) a DNA sequence that is expressed to form a functional product: either RNA or
polypeptide
D) a DNA—RNA sequence combination that results in an enzymatic product
E) a discrete unit of hereditary information that consists of a sequence of amino acids

Answer 10

C) a DNA sequence that is expressed to form a functional product: either RNA or
polypeptide

Question 11

In the polymerization of DNA, a phosphodiester bond is formed between a
phosphate group of the nucleotide being added and ________ of the last nucleotide in
the polymer.
A) the 5’ phosphate
B) C6
C) the 3’ OH
D) a nitrogen from the nitrogen-containing base

Answer 11

C) the 3’ OH

Question 12

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with
thymine and cytosine forms hydrogen bonds with guanine. This arrangement ________.
A) allows variable width of the double helix
B) permits complementary base pairing
C) determines the tertiary structure of a DNA molecule
D) determines the type of protein produced

Answer 12

B) permits complementary base pairing

Question 13

Who performed classic experiments that supported the semiconservative model of
DNA replication?
A) Watson and Crick
B) Meselson and Stahl
C) Hershey and Chase
D) Franklin and Wilkins

Answer 13

B) Meselson and Stahl

Question 14

Semiconservative replication involves a template. What is the template?
A) single-stranded binding proteins
B) DNA polymerase
C) one strand of the DNA molecule
D) an RNA molecule

Answer 14

C) one strand of the DNA molecule

Question 15

DNA is synthesized through a process known as ________.
A) semiconservative replication
B) conservative replication
C) translation
D) transcription

Answer 15

A) semiconservative replication

Question 16

Suppose you are provided with an actively dividing culture of E. coli bacteria to
which radioactive thymine has been added. What would happen if a cell replicates once
in the presence of this radioactive base?
A) One of the daughter cells, but not the other, would have radioactive DNA.
B) Neither of the two daughter cells would be radioactive.
C) All four bases of the DNA would be radioactive.
D) Radioactive thymine would pair with nonradioactive guanine.
E) DNA in both daughter cells would be radioactive.

Answer 16

E) DNA in both daughter cells would be radioactive.

Question 17

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to
grow for two more generations (two rounds of DNA replication). DNA extracted from
these cells is centrifuged. What density distribution of DNA would you expect in this
experiment?
A) one high-density and one low-density band
B) one intermediate-density band
C) one high-density and one intermediate-density band
D) one low-density and one intermediate-density band
E) one low-density band

Answer 17

D) one low-density and one intermediate-density band

Question 18

In the figure associated with this question, which of the three types of viruses shown
would you expect to include a capsid(s)?
A) I only
B) II only
C) III only
D) I and II only
E) I, II, and III

Answer 18

E) I, II, and III

Question 19

DNA contains the template needed to copy itself, but it has no catalytic activity in
cells. What catalyzes the formation of phosphodiester bonds between adjacent
nucleotides in the DNA polymer being formed?
A) ribozymes
B) DNA polymerase
C) ATP
D) deoxyribonucleotide triphosphates

Answer 19

B) DNA polymerase

Question 20

Refer to the figure associated with this question. Which structure is responsible for
stabilizing DNA in its single-stranded form?
A) A
B) B
C) C
D) D

Answer 20

C) C

Question 21

What provides the energy for the polymerization reactions in DNA synthesis?
A) ATP
B) DNA polymerase
C) breaking the hydrogen bonds between complementary DNA strands
D) the deoxyribonucleotide triphosphate substrates

Answer 21

D) the deoxyribonucleotide triphosphate substrates

Question 22

Refer to the figure associated with this question. What bases will be added to the primer
as DNA replication proceeds? The bases should appear in the new strand in the order
that they will be added starting at the 3’ end of the primer.
A) C, A, G, C, A, G, A
B) T, C, T, G, C, T, G
C) A, G, A, C, G, A, C
D) G, T, C, G, T, C, T

Answer 22

C) A, G, A, C, G, A, C

Question 23

Identify the lagging strand during duplication of DNA starting from a double helix in the
accompanying figure.
A) a
B) b
C) c
D) d

Answer 23

C) c

Question 24

Put the following steps of DNA replication in chronological order.
1. Single-stranded binding proteins attach to DNA strands.
2. Hydrogen bonds between base pairs of antiparallel strands are broken.
3. Primase binds to the site of origin.
4. DNA polymerase binds to the template strand.
5. An RNA primer is created.
A) 1, 2, 3, 4, 5
B) 2, 1, 3, 5, 4
C) 3, 2, 1, 5, 4
D) 3, 1, 2, 4, 5

Answer 24

B) 2, 1, 3, 5, 4

Question 25

In the accompanying figure, which is the template strand?
A) a
B) b
C) c
D) d

Answer 25

A) a

Question 26

What is a major difference between eukaryotic DNA replication and prokaryotic DNA
replication?
A) Prokaryotic replication does not require a primer.
B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic
chromosomes have multiple origins of replication.
C) DNA replication in prokaryotic cells is conservative. DNA replication in eukaryotic
cells is semiconservative.
D) DNA polymerases of prokaryotes can add nucleotides to both 3’ and 5’ ends of DNA
strands; those of eukaryotes function only in the 5’ → 3’ direction.

Answer 26

B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have multiple origins of replication.

Question 27

In the accompanying figure, which structure causes the two strands of DNA to
separate?
A) A
B) B
C) C
D) D

Answer 27

B) B

Question 28

At a specific area of a chromosome, the following sequence of nucleotides is
present where the chain opens to form a replication fork:
3’ C C T A G G C t G C A A T C C 5’
An RNA primer is formed starting at the underlined T (T) of the template. Which of the
following represents the primer sequence?
A) 5’ G C C T A G G 3’
B) 3’ G C C T A G G 5’
C) 5’ A C G T T A G G 3’
D) 5’ A C G U U A G G 3’
E) 5’ G C C U A G G 3’

Answer 28

D) 5’ A C G U U A G G 3’

Question 29

Polytene chromosomes of Drosophila salivary glands each consist of multiple
identical DNA strands that are aligned in parallel arrays. How could these arise?
A) replication followed by mitosis
B) replication without separation
C) meiosis followed by mitosis
D) fertilization by multiple sperm
E) special association with histone proteins

Answer 29

B) replication without separation

Question 30

In E. coli, what is the function of DNA polymerase III?
A) to unwind the DNA helix during replication
B) to seal together the broken ends of DNA strands
C) to add nucleotides to the 3’ end of a growing DNA strand
D) to degrade damaged DNA molecules
E) to rejoin the two DNA strands (one new and one old) after replication

Answer 30

C) to add nucleotides to the 3’ end of a growing DNA strand

Question 31

The leading and the lagging strands differ in that ________.
A) the leading strand is synthesized in the same direction as the movement of the
replication fork, and the lagging strand is synthesized in the opposite direction
B) the leading strand is synthesized by adding nucleotides to the 3’ end of the growing
strand, and the lagging strand is synthesized by adding nucleotides to the 5’ end
C) the lagging strand is synthesized continuously, whereas the leading strand is
synthesized in short fragments that are ultimately stitched together
D) the leading strand is synthesized at twice the rate of the lagging strand

Answer 31

A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction

Question 32

What is the role of DNA ligase in the elongation of the lagging strand during DNA
replication?
A) It synthesizes RNA nucleotides to make a primer.
B) It catalyzes the lengthening of telomeres.
C) It joins Okazaki fragments together.
D) It unwinds the parental double helix.
E) It stabilizes the unwound parental DNA.

Answer 32

C) It joins Okazaki fragments together.

Question 33

Which of the following help(s) to hold the DNA strands apart while they are being
replicated?
A) primase
B) ligase
C) DNA polymerase
D) single-strand DNA binding proteins
E) nuclease

Answer 33

D) single-strand DNA binding proteins

Question 34

Eukaryotic telomeres replicate differently than the rest of the chromosomes. This is a consequence of which of the following?
A) the evolution of telomerase enzyme
B) DNA polymerase that cannot replicate the leading strand template to its 5’ end
C) gaps left at the 5’ end of the lagging strand
D) gaps left at the 3’ end of the lagging strand because of the need for a primer
E) the “no ends” of a circular chromosome

Answer 34

C) gaps left at the 5’ end of the lagging strand

Question 35

How does the enzyme telomerase meet the challenge of replicating the ends of
linear chromosomes?
A) It adds a single 5’ cap structure that resists degradation by nucleases.
B) It causes specific double-strand DNA breaks that result in blunt ends on both
strands.
C) It causes linear ends of the newly replicated DNA to circularize.
D) It catalyzes the lengthening of telomeres, compensating for the shortening that could
occur during replication without telomerase activity.
E) It adds numerous GC pairs, which resist hydrolysis and maintain chromosome
integrity.

Answer 35

D) It catalyzes the lengthening of telomeres, compensating for the shortening that could
occur during replication without telomerase activity

Question 36

The DNA of telomeres has been highly conserved throughout the evolution of
eukaryotes. This most likely reflects ________.
A) the inactivity of this region of DNA
B) the low frequency of mutations occurring in this DNA
C) continued evolution of telomeres
D) that new mutations in telomeres have been advantageous
E) a critical function of telomeres

Answer 36

E) a critical function of telomeres

Question 37

Which of the following would you expect of a eukaryote lacking telomerase?
A) a high probability of somatic cells becoming cancerous
B) an inability to produce Okazaki fragments
C) an inability to repair thymine dimers
D) a reduction in chromosome length in gametes
E) high sensitivity to sunlight

Answer 37

D) a reduction in chromosome length in gametes

Question 38

What is a telomere?
A) the mechanism that holds two sister chromatids together
B) DNA replication during telophase
C) the site of origin of DNA replication
D) the ends of linear chromosomes

Answer 38

D) the ends of linear chromosomes

Question 39

Telomere shortening puts a limit on the number of times a cell can divide. Research
has shown that telomerase can extend the life span of cultured human cells. How might
adding telomerase affect cellular aging?
A) Telomerase will speed up the rate of cell proliferation.
B) Telomerase eliminates telomere shortening and retards aging.
C) Telomerase shortens telomeres, which delays cellular aging.
D) Telomerase would have no effect on cellular aging.

Answer 39

B) Telomerase eliminates telomere shortening and retards aging.

Question 40

Which of the following cells have reduced or very little active telomerase activity?
A) most normal somatic cells
B) most normal germ cells
C) most cancer cells
D) None of the above choices is correct.

Answer 40

A) most normal somatic cells

Question 41

Telomere shortening is a problem in which types of cells?
A) only prokaryotic cells
B) only eukaryotic cells
C) cells in prokaryotes and eukaryotes

Answer 41

B) only eukaryotic cells

Question 42

What appears to be a dark side to telomerase activity with regard to human health?
A) Telomerase is active in most cancer cells.
B) Telomerase is inhibited by p53.
C) p53 inhibits telomerase.
D) There are more chromosomal ends than can be repaired by telomerase.
E) Telomerase activity is only seen in somatic cells; therefore, chromosome shortening
is likely in gametic chromosomes.

Answer 42

A) Telomerase is active in most cancer cells.

Question 43

DNA replication is highly accurate. It results in about one mistake per billion
nucleotides. For the human genome, how often would errors occur?
A) on average, once or twice in the lifetime of an individual
B) on average, six times each time the entire genome of a cell is replicated
C) on average, once every six cell divisions
D) on average, once in a lifetime in 10 percent of the population

Answer 43

B) on average, six times each time the entire genome of a cell is replicated

Question 44

In a healthy cell, the rate of DNA repair is equal to the rate of DNA mutation. When
the rate of repair lags behind the rate of mutation, what is a possible fate of the cell?
A) The cell can be transformed to a cancerous cell.
B) RNA may be used instead of DNA as inheritance material.
C) The cell will become embryonic.
D) DNA synthesis will continue by a new mechanism.

Answer 44

A) The cell can be transformed to a cancerous cell.

Question 45

The epsilon (ε) subunit of DNA polymerase III of E. coli has exonuclease activity.
How does it function in the proofreading process? The epsilon subunit ________.
A) removes a mismatched nucleotide
B) excises a segment of DNA around the mismatched base
C) can recognize which strand is the template or parent strand and which is the new
strand of DNA.
D) adds nucleotide triphosphates to the 3’ end of the growing DNA strand

Answer 45

A) removes a mismatched nucleotide

Question 46

Recent studies have shown that xeroderma pigmentosum (an error in the nucleotide
excision repair process) can result from mutations in one of seven genes. What can you
infer from this finding?
A) There are seven genes that produce the same protein.
B) These seven genes are the most easily damaged by ultraviolet light.
C) There are several proteins involved in the nucleotide excision repair process.
D) These mutations have resulted from translocation of gene segments.

Answer 46

C) There are several proteins involved in the nucleotide excision repair process.

Question 47

Researchers found E. coli that had mutation rates 100 times higher than normal.
Which of the following is the most likely cause of these results?
A) The single-stranded binding proteins were malfunctioning.
B) There were one or more mismatches in the RNA primer.
C) The proofreading mechanism of DNA polymerase was not working properly.
D) The DNA polymerase was unable to add bases to the 3’ end of the growing nucleic
acid chain.

Answer 47

C) The proofreading mechanism of DNA polymerase was not working properly.

Question 48

In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision
repair mechanism. These individuals are unable to repair DNA damage caused by
ultraviolet light. Which of the following are the most prominent types of DNA lesions in
individuals suffering from xeroderma pigmentosum?
A) mismatch errors
B) telomere shortening
C) methylation of purines
D) thymine dimers

Answer 48

D) thymine dimers

Question 49

Which one of the following is LEAST likely to cause mutations in DNA?
A) aflatoxins that are found in moldy grains
B) hydroxyl radicals formed as by-products of aerobic respiration
C) ultraviolet radiation from sunlight
D) light from an incandescent bulb

Answer 49

D) light from an incandescent bulb

Question 50

Given the damage caused by UV radiation, the kind of gene affected in those with
XP is one whose product is involved with ________.
A) mending of double-strand breaks in the DNA backbone
B) breakage of cross-strand covalent bonds
C) the ability to excise single-strand damage and replace it
D) the removal of double-strand damaged areas
E) causing affected skin cells to undergo apoptosis

Answer 50

C) the ability to excise single-strand damage and replace it

Question 51

Which of the following contradicts the one-gene, one-enzyme hypothesis?
A) A mutation in a single gene can result in a defective protein.
B) Alkaptonuria results when individuals lack a single enzyme involved in the catalysis
of homogentisic acid.
C) Sickle cell anemia results in defective hemoglobin.
D) A single antibody gene can code for different related proteins, depending on the
splicing that takes place post-transcriptionally.

Answer 51

D) A single antibody gene can code for different related proteins, depending on the
splicing that takes place post-transcriptionally.

Question 52

Which of the following would be LEAST likely to cause DNA damage to an individual
suffering from xeroderma pigmentosum (XP)?
A) direct sunlight
B) tanning beds
C) incandescent lightbulbs
D) reflected sunlight

Answer 52

C) incandescent lightbulbs

Question 53

Beadle and Tatum discovered that metabolic pathways are studied most effectively
using which of the following techniques?
A) using multiple gene mutations resulting in nonfunctional enzymes specific to a
metabolic pathway
B) adding intermediates to a metabolic pathway
C) removing all intermediates of a metabolic pathway
D) using single gene mutations resulting in nonfunctional enzymes specific to a
metabolic pathway

Answer 53

D) using single gene mutations resulting in nonfunctional enzymes specific to a
metabolic pathway

Question 53

Refer to the associated figure. In the branched metabolic pathway indicated in the
figure, if enzyme 3 is defective and the amount of each enzyme is constant, you might
expect to see an increase in the amount of which intermediate or product?
A) E
B) B
C) F
D) D

Answer 53

B) B

Question 54

The proteome is all the proteins produced by an organism. The genome is the totality
of all genes of an organism. If the proteome is much larger than the genome, which of
the following statements would be accurate?
A) This finding lends support to a one-gene, two-enzyme hypothesis.
B) The number of monomeric subunits found in proteins is fewer than the number of
monomeric subunits found in genes.
C) At least in some cases, a single gene must code for more than one protein.
D) Noncoding DNA is important in determining the proteome.

Answer 54

C) At least in some cases, a single gene must code for more than one protein.

Question 55

Refer to the metabolic pathway illustrated in the associated figure. If A, B, and C are all
required for growth, a strain mutant for the gene encoding enzyme B would be able to
grow on medium supplemented with ________.
A) nutrient A only
B) nutrient B only
C) nutrient C only
D) nutrients A and C

Answer 55

C) nutrient C only

Question 56

Which of the following is NOT synthesized from a DNA template?
A) messenger RNA
B) amino acids
C) transfer RNA
D) ribosomal RNA

Answer 56

B) amino acids

Question 57

In the Morse code, a series of dots and dashes code for letters of the alphabet. How
is this analogous to the genetic code?
A) There is complementarity in the genetic code (A is complementary to T, and C is
complementary to G).
B) The bases that make up DNA are coded by the sugar-phosphate backbone.
C) The machinery involved in DNA synthesis is analogous to the telegraph equipment
used in sending Morse code.
D) The bases of DNA code for the more complex amino acid sequence of the proteins
in cells.

Answer 57

D) The bases of DNA code for the more complex amino acid sequence of the proteins
in cells.

Question 57

In the process of transcription, ________.
A) DNA is replicated
B) RNA is synthesized
C) proteins are synthesized
D) mRNA attaches to ribosomes

Answer 57

B) RNA is synthesized

Question 58

Refer to the associated figure. A branched metabolic pathway synthesizes two related
amino acids (D and F). If there is a genetic defect, resulting in a nonfunctional enzyme
(3), how could you ensure that adequate amounts of the amino acid F are synthesized?
A) supplement intermediate B
B) supplement intermediate C
C) add enzyme 2 to the medium
D) supplement with intermediate E

Answer 58

D) supplement with intermediate E

Question 58

According to the table and the figure associated with this question, which enzyme is
defective in the strain with the arg2 mutation?
A) the enzyme that converts the precursor to ornithine
B) the enzyme that converts ornithine to citrulline
C) the enzyme that converts citrulline to arginine
D) the enzyme that converts the precursor to citrulline

Answer 58

B) the enzyme that converts ornithine to citrulline

Question 58

Knockout mice have been genetically altered to knock out specific genes. How are
these mice most often used in research?
A) to study DNA replication in the defective genes (those that have been altered)
B) to determine the role of proteins coded for by those genes that are knocked out
C) to examine defects in DNA structure in those regions that have been altered
D) to study the effect of radiation on DNA

Answer 58

B) to determine the role of proteins coded for by those genes that are knocked out

Question 59

Given the DNA template shown in the associated figure, which of the following bases
would you find in a complementary RNA strand and where would they be synthesized?
A) A-A-A-A-A; nucleus
B) U-U-U-U-U; nucleus
C) A-A-A-A-A; ribosome
D) U-U-U-U-U; ribosome

Answer 59

A) A-A-A-A-A; nucleus

Question 60

In the first step of their experiments, Jacob and Monod treated E. coli cells with
ultraviolet light or X-rays to ________.
A) decrease the rate of gene expression
B) induce DNA repair enzymes
C) increase the frequency of mutations in all genes
D) selectively mutate specific genes, leaving all other genes unmutated

Answer 60

C) increase the frequency of mutations in all genes

Question 60

All three domains (Bacteria, Archaea, and Eukarya) follow the same genetic code.
Therefore, which of the following statements would most likely be correct?
A) The genetic code evolved three times.
B) The genetic code evolved before DNA replaced RNA as the unit of genetic
information.
C) There were no mutations following the evolution of the genetic code.
D) The genetic code evolved before the different domains diverged.

Answer 60

D) The genetic code evolved before the different domains diverged.

Question 60

Genotype is to ________ as phenotype is to ________.
A) DNA base sequence; physical traits that are products of the proteins produced
B) heredity; DNA base sequence
C) gene regulation; translation
D) transcription; amino acid sequence

Answer 60

A) DNA base sequence; physical traits that are products of the proteins produced

Question 61

The statement “DNA → RNA → Proteins” ________.
A) is known as the central dogma
B) depicts the regulation of gene expression
C) is the same in all organisms, as well as viruses and prions
D) describes a series of catalytic reactions

Answer 61

D) describes a series of catalytic reactions

Question 61

Which of the following is an exception to the central dogma?
A) the discovery of RNA viruses that synthesize DNA using reverse transcriptase
B) the discovery that the Archaea and Bacteria are more distantly related than are
Archaea and Eukarya
C) the discovery of ribozymes
D) the discovery of DNA as the unit of genetic inheritance

Answer 61

A) the discovery of RNA viruses that synthesize DNA using reverse transcriptase

Question 62

HIV, the causative agent of AIDS, is a retrovirus. A retrovirus ________.
A) uses DNA as a template in the process of translation
B) makes proteins directly from RNA
C) uses reverse transcriptase to make DNA from RNA
D) is a cellular virus that uses ribosomes to reproduce inside a living cell

Answer 62

C) uses reverse transcriptase to make DNA from RNA

Question 63

Once researchers identified DNA as the unit of inheritance, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. What is the mechanism of information transfer in eukaryotes?
A) DNA from a single gene is replicated and transferred to the cytoplasm, where it
serves as a template for protein synthesis.
B) Messenger RNA is transcribed from a single gene and transfers information from the
DNA in the nucleus to the cytoplasm, where protein synthesis takes place.
C) Proteins transfer information from the nucleus to the ribosome, where protein
synthesis takes place.
D) Transfer RNA takes information from DNA directly to a ribosome, where protein
synthesis takes place.

Answer 63

B) Messenger RNA is transcribed from a single gene and transfers information from the
DNA in the nucleus to the cytoplasm, where protein synthesis takes place.

Question 64

According to the central dogma, what molecule should go in the blank?
DNA → ________ → Proteins
A) mtDNA
B) rRNA
C) mRNA
D) tRNA

Answer 64

C) mRNA

Question 65

How does the simple primary and secondary structure of DNA hold the information
needed to code for the many features of multicellular organisms?
A) The hydrogen bonding among backbone constituents carries coded information.
B) The base sequence of DNA carries the information needed to code for proteins.
C) The width of the double helix changes at each gene due to differences in hydrogen
bonds.
D) The amino acids that make up the DNA molecule contain the information needed to
make cellular proteins.

Answer 65

B) The base sequence of DNA carries the information needed to code for proteins.

Question 66

Use this representation to answer the following question.
DNA template strand 5’ ________ 3’
DNA nontemplate strand 3’ ________ 5’
Given the locally unwound double strand above, in which direction does the RNA
polymerase move while transcribing DNA?
A) 3’ → 5’ along the template DNA strand
B) 5’ → 3’ along the template DNA strand
C) 3’ → 5’ along the nontemplate DNA strand
D) 5’ → 3’ along the nontemplate DNA strand
E) 5’ → 3’ along the double-stranded DNA

Answer 66

B) 5’ → 3’ along the template DNA strand

Question 67

What does it mean when we say the genetic code is redundant?
A) A single codon can specify the addition of more than one amino acid.
B) The genetic code is different for different domains of organisms.
C) The genetic code is universal (the same for all organisms).
D) More than one codon can specify the addition of the same amino acid.

Answer 67

D) More than one codon can specify the addition of the same amino acid.

Question 67

A particular triplet of bases in the template strand of DNA is 5’ AGT 3’. The
corresponding codon for the mRNA transcribed is ________.
A) 3’ UCA 5’
B) 3’ UGS 5’
C) 5’ TCA 3’
D) 3’ ACU 5’
E) either UCA or TCA, depending on wobble in the first base

Answer 67

A) 3’ UCA 5’

Question 68

Which of the following nucleotide triplets best represents a codon?
A) a triplet separated spatially from other triplets
B) a triplet in the middle of a ribosomal RNA molecule
C) a triplet at the opposite end of tRNA from the attachment site of the amino acid
D) a triplet in the same reading frame as an upstream AUG
E) a sequence in tRNA at the 3’ end

Answer 68

D) a triplet in the same reading frame as an upstream AUG

Question 69

The genetic code is essentially the same for all organisms. From this, one can
logically assume which of the following?
A) A gene from an organism can theoretically be expressed by any other organism.
B) All organisms have experienced convergent evolution.
C) DNA was the first genetic material.
D) The same codons in different organisms translate into different amino acids.
E) Different organisms have different types of amino acids.

Answer 69

A) A gene from an organism can theoretically be expressed by any other organism.

Question 70

The “universal” genetic code is now known to have exceptions. Evidence for this
can be found if which of the following is TRUE?
A) if UGA, usually a stop codon, is found to code for an amino acid such as tryptophan
(usually coded for by UGG only) in a different organism
B) if one stop codon, such as UGA, is found to have a different effect on translation than
another stop codon, such as UAA
C) if prokaryotic organisms are able to translate a eukaryotic mRNA and produce the
same polypeptide
D) if several codons are found to translate to the same amino acid, such as serine
E) if a single mRNA molecule is found to translate to more than one polypeptide when
there are two or more AUG sites

Answer 70

A) if UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only) in a different organism

Question 71

Which of the following is directly related to a single amino acid?
A) the base sequence of the tRNA
B) the type of RNA polymerase used to carry out transcription
C) the three-base sequence of mRNA
D) the complementarity of DNA and RNA

Answer 71

C) the three-base sequence of mRNA

Question 72

Codons are part of the molecular structure of ________.
A) a protein
B) mRNA
C) tRNA
D) rRNA

Answer 72

B) mRNA

Question 73

Which of the following observations may have resulted in the hypothesis that a
codon is made up of three bases?
A) A codon of two bases in length, from four different bases, would code for a maximum
of thirty-two different amino acids.
B) A codon of three bases in length, from four different bases, would code for a
maximum of twelve different amino acids.
C) A codon of four bases in length, from four different bases, would code for a
maximum of twenty-four different amino acids.
D) A codon of three bases in length, from four different bases, would code for a
maximum of sixty-four different amino acids.

Answer 73

D) A codon of three bases in length, from four different bases, would code for a
maximum of sixty-four different amino acids.

Question 74

Consider the following section of mRNA:
UCUGAUGGGCUUU…
Beginning with the start codon, which amino acids, in order, are coded for by this
section of mRNA? Consult the codon table provided if necessary.
A) serine, aspartic acid, glycine, leucine
B) methionine, glycine, phenylalanine
C) methionine, valine, glycine, phenylalanine
D) threonine, methionine, glycine

Answer 74

B) methionine, glycine, phenylalanine

Question 75

A possible sequence of nucleotides in the template strand of DNA that would code
for the polypeptide sequence phe-leu-ile-val would be ________.
A) 5’ TTG-CTA-CAG-TAG 3’
B) 3’ AAC-GAC-GUC-AUA 5’
C) 5’ AUG-CTG-CAG-TAT 3’
D) 3’ AAA-AAT-ATA-ACA 5’
E) 3’ AAA-GAA-TAA-CAA 5’

Answer 75

E) 3’ AAA-GAA-TAA-CAA 5’

Question 76

What amino acid sequence will be generated, based on the following mRNA codon
sequence?
5’ AUG-UCU-UCG-UUA-UCC-UUG 3’
A) met-arg-glu-arg-glu-arg
B) met-glu-arg-arg-glu-leu
C) met-ser-leu-ser-leu-ser
D) met-ser-ser-leu-ser-leu
E) met-leu-phe-arg-glu-glu

Answer 76

D) met-ser-ser-leu-ser-leu

Question 77

A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the
following sequences in the coding strand of the DNA could code for this peptide?
A) 3’ UUU-CCC-AAA-GGG-UUU-CCC
B) 3’ AUG-AAA-GGG-TTT-CCC-AAA-GGG
C) 5’ TTT-CCC-AAA-GGG-TTT-CCC
D) 5’ GGG-AAA-TTT-AAA-CCC-ACT-GGG
E) 5’ ACT-TAC-CAT-AAA-CAT-TAC-UGA

Answer 77

C) 5’ TTT-CCC-AAA-GGG-TTT-CCC

Question 78

Which one of the following is TRUE? A codon ________.
A) consists of four nucleotides
B) can code for up to four different amino acids
C) extends from one end of a tRNA molecule
D) is the basic unit of the genetic code

Answer 78

D) is the basic unit of the genetic code

Question 79

Point mutations are referred to as missense, silent, frameshift, or nonsense when
they change the protein-coding potential of a gene. What is another group of mutations
that may have important consequences for gene expression?
A) mutations that exist outside coding sequences
B) combinations of missense and silent mutations
C) combinations of nonsense and silent mutations
D) mutations that alter the amino acid sequence of a gene
E) mutations that shift the reading frame of a gene

Answer 79

A) mutations that exist outside coding sequences

Question 80

The mutation resulting in sickle cell disease changes one base pair of DNA so that a
codon now codes for a different amino acid, making it an example of a ________.
A) nonsense mutation
B) frameshift mutation
C) silent mutation
D) missense mutation

Answer 80

D) missense mutation

Question 80

A mutation that results in premature termination of translation ________.
A) is a silent mutation
B) is a nonsense mutation
C) usually has no effect on the function of the protein
D) is a missense mutation

Answer 80

B) is a nonsense mutation

Question 81

Why might a point mutation in DNA make a difference in the level of a protein’s
activity?
A) It might result in a chromosomal translocation.
B) It might exchange one stop codon for another stop codon.
C) It might delay the rate of DNA replication.
D) It might substitute a different amino acid in the active site.
E) It might substitute the N-terminus of the polypeptide for the C-terminus.

Answer 81

D) It might substitute a different amino acid in the active site.

Question 81

Which of the following types of mutation, resulting in an error in the mRNA just after
the AUG start of translation, is likely to have the most serious effect on the polypeptide
product?
A) a deletion of a codon
B) a deletion of two nucleotides
C) a substitution of the third nucleotide in an ACC codon
D) a substitution of the first nucleotide of a GGG codon
E) an insertion of a codon

Answer 81

B) a deletion of two nucleotides

Question 82

A nonsense mutation in a gene ________.
A) changes an amino acid in the encoded protein
B) has no effect on the amino acid sequence of the encoded protein
C) introduces a premature stop codon into the mRNA
D) alters the reading frame of the mRNA
E) prevents introns from being excised

Answer 82

C) introduces a premature stop codon into the mRNA

Question 83

Which of the following mutations is likely to cause the most dramatic phenotypic
change?
A) a duplication of all or most introns
B) a large inversion whose ends are each in the same region between genes
C) a nucleotide substitution in an exon coding for a transmembrane domain
D) a single nucleotide deletion in an exon coding for an active site
E) a frameshift mutation one codon away from the 3’ end of the nontemplate strand

Answer 83

D) a single nucleotide deletion in an exon coding for an active site

Question 84

A frameshift mutation could result from ________.
A) a base insertion only
B) a base deletion only
C) a base substitution only
D) deletion of three consecutive bases
E) either an insertion or a deletion of a base

Answer 84

E) either an insertion or a deletion of a base

Question 85

Which of the following DNA mutations is most likely to damage the protein it
specifies?
A) a base-pair deletion
B) an addition of three nucleotides
C) a substitution in the last base of a codon
D) a codon deletion

Answer 85

A) a base-pair deletion

Question 86

Which small-scale mutation would be most likely to have a catastrophic effect on the
functioning of a protein?
A) a base substitution
B) a base deletion near the start of a gene
C) a base deletion near the end of the coding sequence, but not in the terminator codon
D) deletion of three bases near the start of the coding sequence, but not in the initiator
codon
E) a base insertion near the end of the coding sequence, but not in the terminator codon

Answer 86

B) a base deletion near the start of a gene

Question 87

The most commonly occurring mutation in people with cystic fibrosis is a deletion of
a single codon. This results in ________.
A) a base-pair substitution
B) a nucleotide mismatch
C) a frameshift mutation
D) a polypeptide missing an amino acid
E) a nonsense mutation

Answer 87

D) a polypeptide missing an amino acid

Question 88

Which of the following mutations would be most likely to have a harmful effect on an
organism?
A) a nucleotide-pair substitution
B) a deletion of three nucleotides near the middle of a gene
C) a single nucleotide deletion in the middle of an intron
D) a single nucleotide deletion near the end of the coding sequence
E) a single

Answer 88

E) a single

Question 89

The associated figure shows a diagram of blocks of genes on human chromosome 16
and the locations of blocks of similar genes on four chromosomes of the mouse.
The movement of these blocks suggests that ________.
A) during evolutionary time, these sequences have separated and have returned to their
original positions
B) DNA sequences within these blocks have become increasingly divergent
C) sequences represented have duplicated at least three times
D) chromosomal translocations have moved blocks of sequences to other
chromosomes
E) higher mammals have more convergence of gene sequences related in function

Answer 89

D) chromosomal translocations have moved blocks of sequences to other
chromosomes

Question 90

In eukaryotes there are several different types of RNA polymerase. Which type is
involved in transcription of mRNA for a globin protein?
A) RNA polymerase I
B) RNA polymerase II
C) RNA polymerase III
D) RNA polymerase IV
E) primase

Answer 90

B) RNA polymerase II

Question 91

Which of the following mutations is most likely to cause a phenotypic change?
A) a duplication of all or most introns
B) a large inversion whose ends are each in the same region between genes
C) a nucleotide substitution in an exon coding for a transmembrane domain
D) a single nucleotide deletion in an exon coding for an active site
E) a frameshift mutation one codon away from the 3’ end of the nontemplate strand

Answer 91

D) a single nucleotide deletion in an exon coding for an active site

Question 92

Which molecule or reaction supplies the energy for polymerization of nucleotides in
the process of transcription?
A) the interaction between RNA polymerase and the promoter
B) the phosphate bonds in the nucleotide triphosphates that serve as substrates
C) the energy released when hydrogen bonds are broken as the DNA molecule is
unwound
D) ATP only

Answer 92

B) the phosphate bonds in the nucleotide triphosphates that serve as substrates

Question 93

Death cap mushrooms produce a substance called alpha-amanitin. Alpha-amanitin
efficiently blocks synthesis of mRNA, but not of tRNA or rRNA, in eukaryotic organisms.
This is possible because alpha-amanitin efficiently interferes with ________.
A) the action of RNA polymerase I, but not RNA polymerase II or III
B) RNA polymerase III, but not RNA polymerase I and II
C) the action of RNA polymerases I and II, but not RNA polymerase III
D) the action of RNA polymerase II, but not RNA polymerase I or III

Answer 93

D) the action of RNA polymerase II, but not RNA polymerase I or III

Question 94

You want to engineer a eukaryotic gene into a bacterial colony and have it
expressed. What must be included in addition to the coding exons of the gene?
A) the introns
B) eukaryotic polymerases
C) a bacterial promoter sequence
D) eukaryotic ribosomal subunits
E) eukaryotic tRNAs

Answer 94

C) a bacterial promoter sequence

Question 95

In eukaryotic cells, transcription cannot begin until ________.
A) the two DNA strands have completely separated and exposed the promoter
B) several transcription factors have bound to the promoter
C) the 5’ caps are removed from the mRNA
D) the DNA introns are removed from the template
E) DNA nucleases have isolated the transcription unit

Answer 95

B) several transcription factors have bound to the promoter

Question 96

In E. coli, if RNA polymerase is missing ________, then transcription initiation would
not occur at the appropriate initiation sites.
A) amino acids
B) mRNA
C) sigma
D) the core enzyme

Answer 96

C) sigma

Question 97

The enzyme complex associated with DNA in the associated figure is ________.
A) helicase
B) DNA polymerase
C) RNA polymerase
D) topoisomerase

Answer 97

C) RNA polymerase

Question 98

David Pribnow studied the base sequences of promoters in bacteria and bacterial
viruses. He found two conserved regions in these promoters (the −10 box and the −35
box). These two regions of the promoter ________.
A) signal the initiation site
B) bind the sigma subunit that is associated with RNA polymerase
C) attach the correct nucleotide triphosphate to the template DNA strand
D) separate the two DNA strands

Answer 98

B) bind the sigma subunit that is associated with RNA polymerase

Question 99

During elongation, RNA polymerase has three prominent channels, or grooves.
These channels provide sites for all of the following EXCEPT ________.
A) a site for the double-stranded DNA molecule
B) a site for the entry of ribonucleoside triphosphates
C) a site for the exit of the diphosphates removed from the nucleotide triphosphates
D) a site for the growing RNA strand

Answer 99

C) a site for the exit of the diphosphates removed from the nucleotide triphosphates

Question 99

Which of the following processes is central to the initiation of transcription in
bacteria?
A) binding of sigma to the promoter region
B) formation of a phosphodiester bond in the elongating RNA strand
C) binding of DNA polymerase to the promoter region
D) formation of a DNA primer

Answer 99

A) binding of sigma to the promoter region

Question 100

What is the function of the group of amino acids on the RNA polymerase, called the
rudder?
A) It provides the energy required for formation of phosphodiester bonds in the
elongating RNA molecule.
B) It helps unwind and open the DNA molecule.
C) It moves template and non-template strands of DNA through channels inside the
enzyme.
D) It helps sigma bind to the RNA polymerase molecule

Answer 100

C) It moves template and non-template strands of DNA through channels inside the
enzyme.

Question 101

Eukaryotes have three nuclear RNA polymerases. The primary function of RNA
polymerase II is transcription of ________.
A) only rRNA-coding genes
B) only tRNA-coding genes
C) both rRNA- and tRNA-coding genes
D) protein-coding genes

Answer 101

D) protein-coding genes

Question 102

Put the following events of bacterial transcription in chronological order.
1. Sigma binds to the promoter region.
2. The double helix of DNA is unwound, breaking hydrogen bonds between
complementary strands.
3. Sigma binds to RNA polymerase.
4. Sigma is released.
5. Transcription begins.
A) 2, 3, 4, 5, 1
B) 2, 3, 1, 4, 5
C) 3, 1, 2, 5, 4
D) 3, 2, 1, 4, 5

Answer 102

C) 3, 1, 2, 5, 4

Question 103

15) How are RNA hairpin turns related to transcriptional termination in E. coli?
A) The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.
B) A three-base repeat signals a stop sequence, and the RNA transcript is released.
C) Release factors bind to sites on the hairpin turn, causing release of the RNA transcript.
D) The hairpin turn prevents more nucleoside triphosphates from entering the active site
of the enzymes, effectively shutting off the process of polymerization.

Answer 103

A) The turns are formed from complementary base pairing and cause separation of the
RNA transcript and RNA polymerase.

Question 104

What is responsible for termination of transcription in eukaryotic protein-coding
genes?
A) a polyadenylation, or poly(A), signal
B) a termination loop composed of guanine
C) a sigma factor
D) a portion of the polymerase holoenzyme
E) three nonsense mutations in sequence

Answer 104

A) a polyadenylation, or poly(A), signal

Question 105

Which one of the following statements about RNA processing is TRUE?
A) Exons are cut out before mRNA leaves the nucleus.
B) Ribozymes may function in RNA splicing.
C) RNA splicing can be catalyzed by tRNA.
D) A primary transcript is often much shorter than the final RNA molecule that leaves
the nucleus.

Answer 105

B) Ribozymes may function in RNA splicing.

Question 106

A ribozyme is ________.
A) a catalyst that uses RNA as a substrate
B) an RNA with catalytic activity
C) an enzyme that catalyzes the association between the large and small ribosomal
subunits
D) an enzyme that synthesizes RNA as part of the transcription process
E) an enzyme that synthesizes RNA primers during DNA replication

Answer 106

B) an RNA with catalytic activity

Question 107

In an experimental situation, a student researcher inserts an mRNA molecule into a
eukaryotic cell after she has removed its 5’ cap and poly-A tail. Which of the following
would you expect her to find?
A) The mRNA is quickly converted into a ribosomal subunit.
B) The cell adds a new poly-A tail to the mRNA.
C) The mRNA attaches to a ribosome and is translated, but more slowly.
D) The molecule is digested by enzymes because it is not protected at the 5’ end

Answer 107

D) The molecule is digested by enzymes because it is not protected at the 5’ end

Question 108

Use this model of a eukaryotic transcript to answer the following question(s).
E = exon and I = intron
5’ UTR E1 I1 E2 I2 E3 I3 E4 UTR 3’
20) Which components of the previous molecule will also be found in mRNA in the cytosol?
A) 5’ UTR I1 I2 I3 UTR 3’
B) 5’ E1 E2 E3 E4 3’
C) 5’ UTR E1 E2 E3 E4 UTR 3’
D) 5’ I1 I2 I3 3’
E) 5’ E1 I1 E2 I2 E3 I3 E4 3

Answer 108

C) 5’ UTR E1 E2 E3 E4 UTR 3’

Question 109

When the spliceosome binds to the transcript shown above, it can attach ________.
A) to the exons
B) to the 5’ UTR
C) to the 3’ UTR
D) at certain sites along an intron

Answer 109

D) at certain sites along an intron

Question 110

Suppose that an induced mutation removes most of the 5’ end of the 5’ UTR of an
mRNA. What is most likely to happen?
A) Removal of the 5’ UTR will have no effect because the exons are still maintained.
B) Removal of the 5’ UTR also removes the 5’ cap and the mRNA will quickly degrade.
C) The 3’ UTR will duplicate and one copy will replace the 5’ end.
D) The first exon will not be read because I1 will now serve as the UTR.

Answer 110

B) Removal of the 5’ UTR also removes the 5’ cap and the mRNA will quickly degrade.

Question 111

As scientists were unraveling the mysteries associated with transcription and
translation in eukaryotes, they discovered there was not a one-to-one correspondence between the nucleotide sequence of a gene and the base sequence of the mRNA it codes for. They proposed the genes-in-pieces hypothesis. How can the genes-in-pieces hypothesis be explained?
A) Introns are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing.
B) Introns are noncoding segments of DNA that are not read or transcribed by RNA polymerase II.
C) Exons are noncoding segments of DNA that are not read or transcribed by RNA
polymerase II.
D) Exons are noncoding segments of DNA that are present in the initial transcript but
are removed by splicing.

Answer 111

A) Introns are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing.

Question 112

What molecules in the spliceosome catalyze the intron removal reactions?
A) RNA polymerases
B) ribozymes
C) tRNA
D) introns

Answer 112

B) ribozymes

Question 113

Some viruses can be crystallized and their structures analyzed. One such virus is
yellow mottle virus, which infects beans. This virus has a single-stranded RNA genome
containing about 6300 nucleotides. Its capsid is 25—30 nm in diameter and contains
180 identical capsomeres. If the yellow mottle virus begins its infection of a cell by using
its genome as mRNA, which of the following would you expect to be able to measure?
A) replication rate
B) transcription rate
C) translation rate
D) accumulation of new ribosomes
E) formation of new transcription factors

Answer 113

C) translation rate

Question 114

Codons are three-base sequences that specify the addition of a single amino acid.
How do eukaryotic codons and prokaryotic codons compare?
A) Prokaryotic codons usually contain different bases than those of eukaryotes.
B) Prokaryotic codons usually specify different amino acids than those of eukaryotes.
C) The translation of codons is mediated by tRNAs in eukaryotes, but translation
requires no intermediate molecules such as tRNAs in prokaryotes.
D) Codons are a nearly universal language among all organisms.

Answer 114

D) Codons are a nearly universal language among all organisms.

Question 115

There should be a strong positive correlation between the rate of protein synthesis
and ________.
A) the quantity of DNA polymerase
B) the quantity of RNA polymerase
C) the size of mRNA
D) the number of ribosomes

Answer 115

D) the number of ribosomes

Question 116

Ribosomes can attach to prokaryotic messenger RNA ________.
A) once post-transcriptional modification is complete
B) before transcription is complete
C) once replication is complete
D) once the primary transcript has been released from RNA polymerase

Answer 116

B) before transcription is complete

Question 117

Which of the following occurs in prokaryotes but not in eukaryotes?
A) post-transcriptional splicing
B) concurrent transcription and translation
C) translation in the absence of a ribosome
D) gene regulation

Answer 117

B) concurrent transcription and translation

Question 118

Which of the following statements is TRUE about protein synthesis in prokaryotes?
A) Extensive RNA processing is required before prokaryotic transcripts can be
translated.
B) Translation can begin while transcription is still in progress.
C) Prokaryotic cells have complicated mechanisms for targeting proteins to the
appropriate cellular organelles.
D) Translation requires antibiotic activity.
E) Unlike eukaryotes, prokaryotes require no initiation or elongation factors

Answer 118

B) Translation can begin while transcription is still in progress.

Question 119

In comparing DNA replication with RNA transcription in the same eukaryotic cell,
only DNA replication ________.
A) uses RNA polymerase
B) makes a new molecule from its 5’ end to its 3’ end
C) occurs in the nucleus of the cell
D) incorporates the entire template molecule in the product

Answer 119

D) incorporates the entire template molecule in the product

Question 120

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon
on the tRNA that binds the mRNA codon is ________.
A) TTT
B) UUA
C) UUU
D) AAA

Answer 120

D) AAA

Question 121

Accuracy in the translation of mRNA into the primary structure of a polypeptide
depends on specificity in the ________.
A) binding of ribosomes to mRNA
B) shape of the A and P sites of ribosomes
C) binding of the anticodon to a small subunit of the ribosome
D) attachment of amino acids to rRNAs
E) binding of the anticodon to the codon and the attachment of amino acids to tRNAs

Answer 121

E) binding of the anticodon to the codon and the attachment of amino acids to tRNAs

Question 122

A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a
lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The
consequence of this for the cell will be that ________.
A) none of the proteins in the cell will contain phenylalanine
B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions
specified by the codon UUU
C) the cell will compensate for the defect by attaching phenylalanine to tRNAs with
lysine-specifying anticodons
D) the ribosome will skip a codon every time a UUU is encountered

Answer 122

B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions
specified by the codon UUU

Question 123

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is
best explained by the fact that ________.
A) some tRNAs have anticodons that recognize 4 or more different codons
B) the rules for base pairing between the third base of a codon and tRNA are flexible
C) many codons are never used, so the tRNAs that recognize them are dispensable
D) the DNA codes for all 61 tRNAs, but some are then destroyed
E) competitive exclusion forces some tRNAs to be destroyed by nucleases

Answer 123

B) the rules for base pairing between the third base of a codon and tRNA are flexible

Question 124

An experimenter has altered the 3’ end of the tRNA corresponding to the amino acid
methionine in such a way as to remove the 3’ bases AC. Which of the following
hypotheses describes the most likely result?
A) tRNA will not form a cloverleaf.
B) The amino acid methionine will not become covalently bound.
C) The anticodon will not bind with the mRNA codon.
D) The aminoacyl-tRNA synthetase will not be formed.

Answer 124

B) The amino acid methionine will not become covalently bound.

Question 125

What ensures that the correct amino acid is added during translation?
A) the anticodon of a properly formed aminoacyl tRNA
B) the methyl-guanosine cap of a properly modified mRNA
C) the poly-A tail of a properly modified mRNA
D) the twisting number of a properly supercoiled DNA

Answer 125

A) the anticodon of a properly formed aminoacyl tRNA

Question 126

If the sequence in the coding strand of DNA for a particular amino acid is 5’AGT3’,
then the anticodon on the corresponding tRNA would be ________.
A) 5’ACU3’
B) 5’TCA3’
C) 5’UCA3’
D) 5’AGU3’

Answer 126

A) 5’ACU3’

Question 127

There are 61 codons that each specify the addition of a specific amino acid, and 3
stop codons for which there is no corresponding amino acid. However, there are only
about 40 tRNA molecules, representing 40 anticodons. How is that possible?
A) Only about 40 of the recognized 61 codons are present in mRNA.
B) An anticodon forms hydrogen bonds with the codon; it must match the first two bases
of the codon but is less specific with respect to the third base.
C) There are tRNAs that can bind one of two related amino acids.
D) Only 20 of the codons are active–one for each amino acid.

Answer 127

B) An anticodon forms hydrogen bonds with the codon; it must match the first two bases
of the codon but is less specific with respect to the third base.

Question 128

In the figure associated with this question, what is the function of the AGU on the
loop of the tRNA?
A) It attaches to the amino acid.
B) It base pairs with a codon of mRNA.
C) It stabilizes the tRNA-amino acid complex.
D) It is the active site of this ribozyme.

Answer 128

B) It base pairs with a codon of mRNA.

Question 129

In the figure associated with this question, what is the function of the ACC sequence
at the 3’ end?
A) It attaches to an amino acid.
B) It base pairs with the codon of mRNA.
C) It stabilizes the tRNA-amino acid complex.
D) It is the active site of this ribozyme.

Answer 129

A) It attaches to an amino acid.

Question 130

A part of an mRNA molecule with the following sequence is being read by a ribosome:
5’ CCG-ACG 3’(mRNA). The following charged transfer RNA molecules (with their
anticodons shown in the 3’ to 5’ direction) are available. Two of them can correctly
match the mRNA so that a dipeptide can form.
The anticodon loop of the first tRNA that will complement this mRNA is
A) 3’ GGC 5’
B) 5’ GGC 3’
C) 5’ ACG 3’
D) 5’ UGC 3’
E) 3’ UGC 5’

Answer 130

A) 3’ GGC 5’

Question 131

The figure associated with this question represents a tRNA that recognizes and
binds a particular amino acid (in this instance, phenylalanine). Which codon on the
mRNA strand codes for this amino acid?
A) UGG
B) GUG
C) GUA
D) UUC
E) CAU

Answer 131

D) UUC

Question 132

The tRNA shown with the previous question has its 3’ end projecting beyond its 5’
end. What will occur at this 3’ end?
A) The codon and anticodon complement one another.
B) The amino acid binds covalently.
C) The excess nucleotides (ACCA)
will be cleaved off at the ribosome.
D) The small and large subunits of the ribosome will attach to it.
E) The 5’ cap of the mRNA will become covalently bound.

Answer 132

B) The amino acid binds covalently.

Question 133

What type of bonding is responsible for maintaining the shape of the tRNA molecule
shown in the figure above?
A) covalent bonding between sulfur atoms
B) ionic bonding between phosphates
C) hydrogen bonding between base pairs
D) van der Waals interactions between hydrogen atoms
E) peptide bonding between amino acids

Answer 133

C) hydrogen bonding between base pairs

Question 134

The anticodon of a particular tRNA molecule is ________.
A) complementary to the corresponding mRNA codon
B) complementary to the corresponding triplet in rRNA
C) the part of tRNA that bonds to a specific amino acid
D) changeable, depending on the amino acid that attaches to the tRNA
E) catalytic, making the tRNA a ribozyme

Answer 134

A) complementary to the corresponding mRNA codon

Question 135

Translation directly involves ________.
A) mRNA, tRNA, GTP, and DNA
B) mRNA, tRNA, ribosomes, and DNA
C) mRNA, ribosomes, GTP, and DNA
D) mRNA, tRNA, ribosomes, and GTP
E) tRNA, ribosomes, GTP, and DNA

Answer 135

D) mRNA, tRNA, ribosomes, and GTP

Question 136

A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine
binds to the growing polypeptide on the other tRNA (#2) in the ribosome already.
Which component of the complex described enters the exit tunnel in the large
subunit of the ribosome?
A) tRNA with attached lysine (#1)
B) tRNA with polypeptide (#2)
C) tRNA that no longer has attached amino acid
D) newly formed polypeptide
E) initiation and elongation factors

Answer 136

D) newly formed polypeptide

Question 137

Where does tRNA #2 move to after this bonding of lysine to the polypeptide?
A) A site
B) P site
C) E site
D) exit tunnel
E) directly to the cytosol

Answer 137

C) E site

Question 138

Which of the following is the first event to take place in translation in eukaryotes?
A) elongation of the polypeptide
B) base pairing of activated methionine-tRNA to AUG of the messenger RNA
C) binding of the larger ribosomal subunit to smaller ribosomal subunits
D) covalent bonding between the first two amino acids
E) the small subunit of the ribosome recognizing and attaching to the 5’ cap of mRNA

Answer 138

E) the small subunit of the ribosome recognizing and attaching to the 5’ cap of mRNA

Question 139

During elongation, which site in the ribosome represents the location where a codon
is being read?
A) E site
B) P site
C) A site
D) the small ribosomal subunit

Answer 139

C) A site

Question 140

Translation requires ________.
A) mRNA, tRNA, DNA, and rRNA
B) mRNA, DNA, and rRNA
C) mRNA, tRNA, and rRNA
D) mRNA, tRNA, and DNA

Answer 140

C) mRNA, tRNA, and rRNA

Question 141

Once a peptide bond has been formed between the amino acid attached to the
tRNA in the P site and the amino acid associated with the tRNA in the A site, what
occurs next?
A) translocation
B) reading of the next codon of mRNA
C) initiation
D) breaking the codon—anticodon hydrogen bonds holding the tRNA in the A site

Answer 141

A) translocation

Question 142

Which of the following, if missing, would usually prevent translation from starting in
eukaryotes?
A) exon
B) 5’ cap
C) AUG codon
D) 5’ cap or AUG codon
E) exon, 5’ cap, or AUG codon

Answer 142

D) 5’ cap or AUG codon

Question 143

The ribosome-binding site of prokaryotes is also known as the ________.
A) TATA box
B) promoter
C) Shine—Dalgarno sequence
D) Pribnow box

Answer 143

C) Shine—Dalgarno sequence

Question 144

Which of the following levels of gene expression allows the most rapid response to
environmental change?
A) transcriptional control
B) translational control
C) post-translational control

Answer 144

C) post-translational control

Question 145

Bacterial and eukaryotic cells primarily control gene expression at the level of
transcription. If instead cells exerted control of gene expression primarily at the posttranslational level, what would be different?
A) The ability to rapidly respond to environmental change would be reduced.
B) Cells would expend significantly more energy.
C) Genes would no longer be transcribed.
D) Translation of mRNA into protein would not occur.

Answer 145

B) Cells would expend significantly more energy.

Question 146

Although the expression of most genes is tightly regulated, some genes are
expressed at roughly constant rates. Which of the following genes would you predict to
be constitutively (constantly) expressed?
A) genes involved in the biosynthesis of the amino acid tryptophan
B) genes involved in the degradation of tryptophan
C) genes involved in the degradation of arabinose, a sugar
D) genes that code for regulatory proteins

Answer 146

D) genes that code for regulatory proteins

Question 147

The greatest expression of the lac operon occurs when lactose levels are ________.
A) low and glucose levels are low
B) low and glucose levels are high
C) high and glucose levels are low
D) high and glucose levels are high

Answer 147

C) high and glucose levels are low

Question 148

Imagine that you have set up a genetic screen to identify E. coli mutants that cannot
metabolize the amino acid tryptophan for energy. Beginning with a master plate
containing many colonies, you prepare replica plates on medium with glucose or
tryptophan as the only energy source. You would look for colonies that ________.
A) cannot grow on either type of media
B) can grow on both types of media
C) can grow only on the plates with tryptophan
D) can grow only on the plates with glucose

Answer 148

D) can grow only on the plates with glucose

Question 150

In the first step of their experiments, Jacob and Monod treated E. coli cells with
ultraviolet light or X-rays to ________.
A) decrease the rate of gene expression
B) induce DNA repair enzymes
C) increase the frequency of mutations in all genes
D) selectively mutate the lac operon, leaving all other genes unmutated

Answer 150

C) increase the frequency of mutations in all genes

Question 150

A compound known as X-gal is widely used in molecular genetic research. When
wild-type (normal) E. coli is grown on medium containing X-gal, the bacterial colonies
turn blue. In contrast, when lacZ mutants are grown on medium containing X-gal, the
bacterial colonies remain their normal white color. X-gal is likely to be a compound
________.
A) chemically similar to glucose
B) chemically similar to galactose
C) chemically similar to lactose
D) that cannot be transported into lacZ mutants
E) that can be transported only into lacA mutants

Answer 150

C) chemically similar to lactose

Question 151

An E. coli cell without a functional lacI gene is expected to ________.
A) never produce β-galactosidase
B) always produce β-galactosidase
C) be unable to transport lactose into the cell
D) be unable to metabolize lactose within the cell

Answer 151

B) always produce β-galactosidase

Question 152

Which of the following, when taken up by a cell, binds to a repressor so that the
repressor no longer binds to the operator?
A) ubiquitin
B) inducer
C) promoter
D) repressor
E) corepressor

Answer 152

B) inducer

Question 153

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E.
coli cell is presented for the first time with the sugar lactose (containing allolactose) as a
potential food source. Which of the following occurs when lactose enters the cell?
A) The repressor protein attaches to the regulator.
B) Allolactose binds to the repressor protein.
C) Allolactose binds to the regulator gene.
D) The repressor protein and allolactose bind to RNA polymerase.
E) RNA polymerase attaches to the regulator.

Answer 153

B) Allolactose binds to the repressor protein.

Question 154

In negative control, a gene is switched off when ________.
A) a kinase adds a phosphate to DNA
B) lactose is transported into the cell
C) a regulatory protein binds to DNA and shuts down transcription
D) a regulatory protein is removed from DNA and shuts down transcription

Answer 154

C) a regulatory protein binds to DNA and shuts down transcription

Question 155

The product of the lacI gene functions most like a car’s ________.
A) parking brake
B) accelerator pedal
C) steering wheel
D) engine
E) gear shift

Answer 155

A) parking brake

Question 156

Suppose several genes are grouped together in a bacterial genome and the group
results in a single enzyme. If one of these genes is mutated and the enzyme is no
longer active, this gene must be part of ________.
A) an intron
B) an operon
C) a repressor
D) an activator
E) an inducer

Answer 156

B) an operon

Question 157

If you wanted to prevent a regulatory protein from changing gene expression, you
would have to prevent physical contact between the protein and ________.
A) ribosomes
B) DNA
C) ribozymes
D) mRNA

Answer 157

B) DNA

Question 158

Jacob and Monod were intellectually primed to draw the conclusions they did
concerning regulation of the lac operon. In part, this was due to their fascination with
mechanisms of enzyme regulation. They knew that the activity of some enzymes is
regulated when their reaction product binds to the enzyme, changing its shape and,
therefore, its activity. This knowledge allowed them to easily make the intellectual leap
to propose ________.
A) the existence of the CAP binding site
B) allosteric regulation of the repressor
C) positive regulation of the lac operon
D) the existence of the operator
E) co-transcribed and co-regulated genes of bacterial operons

Answer 158

B) allosteric regulation of the repressor

Question 158

According to the lac operon model proposed by Jacob and Monod, what is predicted
to occur if the operator is removed from the operon?
A) The lac operon would be transcribed continuously.
B) Only lacZ would be transcribed.
C) Only lacY would be transcribed.
D) Galactosidase permease would be produced but would be incapable of transporting
lactose.

Answer 158

A) The lac operon would be transcribed continuously.

Question 159

The product of the lacI gene is ________.
A) an enzyme
B) a transport protein embedded within the membrane
C) β-galactosidase
D) the repressor

Answer 159

D) the repressor

Question 159

Which of the following is a protein produced by a regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor
E) corepressor

Answer 159

D) repressor

Question 160

Most repressor proteins are allosteric. Which of the following binds with the
repressor to alter its conformation?
A) inducer
B) promoter
C) RNA polymerase
D) transcription factor
E) cAMP

Answer 160

A) inducer

Question 161

There is a mutation in the repressor that results in a molecule known as a superrepressor because it represses the lac operon permanently. Which of these would
characterize such a mutant?
A) It cannot bind to the operator.
B) It cannot make a functional repressor.
C) It cannot bind to the inducer.
D) It makes molecules that bind to one another.
E) It makes a repressor that binds CAP.

Answer 161

C) It cannot bind to the inducer.

Question 162

If she moves the promoter for the lac operon to the region between the beta
galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would
be likely?
A) The three structural genes will be expressed normally.
B) RNA polymerase will no longer transcribe permease.
C) The operon will still transcribe the lacZ and lacY genes, but the mRNA will not be
translated.
D) Beta galactosidase will not be produced.
E) The cell will continue to metabolize but more slowly.

Answer 162

D) Beta galactosidase will not be produced.

Question 163

f she moves the operator to the far end of the operon, past the transacetylase
(lacA) gene, which of the following would likely occur when the cell is exposed to
lactose?
A) The inducer will no longer bind to the repressor.
B) The repressor will no longer bind to the operator.
C) The operon will never be transcribed.
D) The structural genes will be transcribed continuously.
E) The repressor protein will no longer be produced.

Answer 163

D) The structural genes will be transcribed continuously.

Question 164

f she moves the repressor gene (lacI), along with its promoter, to a position at some
several thousand base pairs away from its normal position, we would expect the
________.
A) repressor will no longer be made
B) repressor will no longer bind to the operator
C) repressor will no longer bind to the inducer
D) lac operon will be expressed continuously
E) lac operon will function normally

Answer 164

E) lac operon will function normally

Question 165

The arabinose operon (ara) provides a particularly interesting example of ________
in that when arabinose is present in the environment, the operon is transcribed.
A) positive control
B) negative control
C) push forward control
D) reverse transcription
E) positive translation

Answer 165

A) positive control

Question 166

Under what condition is the AraC protein an activator?
A) The AraC protein is an activator when it is bound to glucose.
B) The AraC protein is an activator when it is bound to lactose.
C) The AraC protein is an activator when it is bound to arabinose.
D) The AraC protein is an activator when it is bound to cyclic AMP.
E) The AraC protein is an activator when it is bound to any sugar molecule.

Answer 166

C) The AraC protein is an activator when it is bound to arabinose.

Question 167

One interesting and surprising finding regarding the regulation of the ara operon is
that it is under both positive and negative control. What protein is responsible for the
dual action of this operon?
A) AraC is responsible for both the positive and negative control of the ara operon.
B) RNA polymerase is responsible for both the positive and negative control of the ara
operon.
C) AraD is responsible for both the positive and negative control of the ara operon.
D) DNA polymerase is responsible for both the positive and negative control of the ara
operon.
E) AraBAD is responsible for both the positive and negative control of the ara operon.

Answer 167

A) AraC is responsible for both the positive and negative control of the ara operon.

Question 168

When many genes of an organism are globally regulated, those genes are
considered as regulon genes. What is the common theme of such genetic regulation?
A) Genes of regulons are silenced by a common repressor.
B) Genes of regulons are able to transcribe mRNA independent of regulation.
C) Genes of regulons are much more stable than non-regulon genes.
D) Genes of regulons are much less stable than non-regulon genes.
E) Individual genes of regulons are regulated independently of each other.

Answer 168

A) Genes of regulons are silenced by a common repressor.

Question 169

In what general way are regulons regulated?
A) Regulons can be under either positive or negative control.
B) Regulons are under negative control exclusively.
C) Regulons are under positive control exclusively.
D) Global regulation of regulons depends on the regulatory guidance of RNA
polymerase II.
E) Regulons are regulated by feedback translation loops

Answer 169

A) Regulons can be under either positive or negative control.