Biology Finals Flashcards


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1

Gases are exchanged in a mammalian embryo in the
A) amnion.
B) hypoblast.
C) chorion.
D) trophoblast.
E) yolk sac.

Answer: C

chorion

2

One hereditary disease in humans, called xeroderma pigmentosum (XP), makes homozygous individuals exceptionally susceptible to UV-induced mutation damage in the cells of exposed tissue, especially skin. Without extraordinary avoidance of sunlight exposure, patients soon succumb to numerous skin cancers.

80) Which of the following best describes this phenomenon?
A) inherited cancer taking a few years to be expressed
B) embryonic or fetal cancer
C) inherited predisposition to mutation
D) inherited inability to repair UV-induced mutation
E) susceptibility to chemical carcinogens

Answer: D

inherited inability to repair UV-induced mutation

3

Genomic imprinting, DNA methylation, and histone acetylation are all examples of
A) genetic mutation.
B) chromosomal rearrangements.
C) karyotypes.
D) epigenetic phenomena.
E) translocation.

Answer: D

epigenetic phenomena

4

Which of the following genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo?
A) homeotic genes
B) segmentation genes
C) egg-polarity genes
D) morphogens
E) inducers

Answer: B

segmentation genes

5

The formation of the fertilization membrane requires an increase in the availability of
A) bicarbonate ions.
B) calcium ions.
C) hydrogen ions.
D) potassium ions.
E) sodium ions.

Answer: B

calcium ions

6

Cells move to new positions as an embryo establishes its three germ tissue layers during
A) determination.
B) cleavage.
C) fertilization.
D) induction.
E) gastrulation.

Answer: E

gastrulation

7

Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell?
A) enzymatic shortening of the poly(A) tail
B) removal of the 5ʹ cap
C) methylation of C nucleotides
D) memethylation of histones
E) removal of one or more exons

Answer B

removal of the 5ʹ cap

8

The lactose operon is likely to be transcribed when
A) there is more glucose in the cell than lactose. B) the cyclic AMP levels are low.
C) there is glucose but no lactose in the cell.
D) the cyclic AMP and lactose levels are both high within the cell.
E) the cAMP level is high and the lactose level is low.

Answer D

the cyclic AMP and lactose levels are both high within the cell

9

Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?
A) morphogenesis
B) determination
C) induction
D) differentiation
E) pattern formation

Answer: E

pattern formation

10

For a repressible operon to be transcribed, which of the following must occur?
A) A corepressor must be present.
B) RNA polymerase and the active repressor must be present.
C) RNA polymerase must bind to the promoter, and the repressor must be inactive.
D) RNA polymerase cannot be present, and the repressor must be inactive.
E) RNA polymerase must not occupy the promoter, and the repressor must be inactive.

Answer: C

RNA polymerase must bind to the promoter, and the repressor must be inactive

11

In placental mammals, the yolk sac
A) transfers nutrients from the yolk to the embryo.
B) differentiates into the placenta.
C) becomes a fluid-filled sac that surrounds and protects the embryo.
D) produces blood cells that then migrate into the embryo.
E) stores waste products from the embryo until the placenta develops.

Answer D

produces blood cells that then migrate into the embryo

12

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

Answer: B

inducer

13

A human blastomere is
A) an embryonic cell that is much smaller than the ovum.
B) an embryonic structure that includes a fluid-filled cavity.
C) that part of the acrosome that opens the egg's membrane.
D) a component of the zona pellucida.
E) a cell that contains a (degenerating) second polar body.

Answer: A

an embryonic cell that is much smaller than the ovum

14

Human trophoblasts
A) form the inner cell mass.
B) form from ectoderm.
C) are the precursors of the mesoderm.
D) are of embryonic origin and function in embryo nutrition.
E) are of maternal origin and function in embryo gas exchange.

Answer: D

are of embryonic origin and function in embryo nutrition

15

In animals, embryonic stem cells differ from adult stem cells in that
A) embryonic stem cells are totipotent, and adult stem cells are pluripotent.
B) embryonic stem cells are pluripotent, and adult stem cells are totipotent.
C) embryonic stem cells have more genes than adult stem cells.
D) embryonic stem cells have fewer genes than adult stem cells.
E) embryonic stem cells are localized to specific sites within the embryo, whereas adult stem cells are spread throughout the body.

Answer: A

embryonic stem cells are totipotent, and adult stem cells are pluripotent.

16

The outer-to-inner sequence of tissue layers in a post-gastrulation vertebrate embryo is
A) endoderm → ectoderm → mesoderm.
B) mesoderm → endoderm → ectoderm.
C) ectoderm → mesoderm → endoderm.
D) ectoderm → endoderm → mesoderm.
E) endoderm → mesoderm → ectoderm.

Answer: C

ectoderm → mesoderm → endoderm.

17

In humans, identical twins are possible because
A) of the heterogeneous distribution of cytoplasmic determinants in unfertilized eggs.
B) of interactions between extraembryonic cells and the zygote nucleus.
C) of convergent extension.
D) early blastomeres can form a complete embryo if isolated.
E) the gray crescent divides the dorsal-ventral axis into new cells.

Answer: D

early blastomeres can form a complete embryo if isolated

18

Two potential devices that eukaryotic cells use to regulate transcription are
A) DNA methylation and histone amplification.
B) DNA amplification and histone methylation.
C) DNA acetylation and methylation.
D) DNA methylation and histone modification.
E) histone amplification and DNA acetylation.

Answer: D

DNA methylation and histone modification

19

The vegetal pole of the zygote differs from the animal pole in that
A) the vegetal pole has a higher concentration of yolk.
B) the blastomeres originate only in the vegetal pole.
C) the posterior end of the embryo forms at the vegetal pole.
D) the vegetal pole cells undergo mitosis but not cytokinesis.
E) the polar bodies bud from this region.

Answer: A

the vegetal pole has a higher concentration of yolk

20

At the moment of sperm penetration, human eggs
A) have used flagellar propulsion to move from the ovary to the oviduct.
B) accept as many sperm as possible in order to select the one with the highest fertility.
C) are still located within the ovary.
D) have a paper-thin cell of calcium carbonate that prevents desiccation.
E) are still surrounded by follicular cells.

Answer: E

are still surrounded by follicular cells

21

The tryptophan operon is a repressible operon that is
A) permanently turned on.
B) turned on only when tryptophan is present in the growth medium.
C) turned off only when glucose is present in the growth medium.
D) turned on only when glucose is present in the growth medium.
E) turned off whenever tryptophan is added to the growth medium.

Answer: E

turned off whenever tryptophan is added to the growth medium

22

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

Answer: D

repressor

23

From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?
A) first cell division → synthesis of embryo's DNA begins → acrosomal reaction → cortical reaction
B) cortical reaction → synthesis of embryo's DNA begins → acrosomal reaction → first cell division
C) cortical reaction → acrosomal reaction → first cell division → synthesis of embryo's DNA begins
D) first cell division → synthesis of embryo's DNA begins → acrosomal reaction → cortical reaction
E) acrosomal reaction → cortical reaction → synthesis of embryo's DNA begins → first cell division

Answer: E

acrosomal reaction → cortical reaction → synthesis of embryo's DNA begins → first cell division

24

In all vertebrate animals, development requires
A) a large supply of yolk.
B) an aqueous environment.
C) extraembryonic membranes.
D) an amnion.
E) a primitive streak.

Answer: B

an aqueous environment

25

One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs?
A) exploring a way to turn on the expression of pseudogenes
B) targeting siRNAs to disable the expression of an allele associated with autosomal recessive disease
C) targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease
D) creating knock-out organisms that can be useful for pharmaceutical drug design
E) looking for a way to prevent viral DNA from causing infection in humans

Answer: C

targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease

26

Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo
A) mitosis.
B) depolarization.
C) apoptosis.
D) vitellogenesis.
E) the acrosomal reaction.

Answer: E

the acrosomal reaction

27

The role of a metabolite that controls a repressible operon is to
A) bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.
B) bind to the operator region and block the attachment of RNA polymerase to the promoter.
C) increase the production of inactive repressor proteins.
D) bind to the repressor protein and inactivate it.
E) bind to the repressor protein and activate it.

Answer: E

bind to the repressor protein and activate it.

28

At the time of implantation, the human embryo is called a
A) blastocyst.
B) gastrula.
C) fetus.
D) somite.
E) zygote.

Answer: A

blastocyst

29

A human zygote undergoes its first cell division
A) 5 seconds after fertilization.
B) 30 minutes after fertilization.
C) 90 minutes after fertilization.
D) 4 hours after fertilization.
E) 24 hours after fertilization.

Answer: E

24 hours after fertilization

30

One of the human leukemias, called CML (chronic myelogenous leukemia), is associated with a chromosomal translocation between chromosomes 9 and 22 in somatic cells of bone marrow. Which of the following allows CML to provide further evidence of this multistep nature of cancer?
A) CML usually occurs in more elderly persons (late age of onset).
B) The resulting chromosome 22 is abnormally short; it is then known as the Philadelphia chromosome.
C) The translocation requires breaks in both chromosomes 9 and 22, followed by fusion between the reciprocal pieces.
D) CML involves a proto-oncogene known as abl.
E) CML can usually be treated by chemotherapy.

Answer: C

The translocation requires breaks in both chromosomes 9 and 22, followed by fusion between the reciprocal pieces.

31

The product of the bicoid gene in Drosophila provides essential information about
A) lethal genes.
B) the dorsal-ventral axis.
C) the left-right axis.
D) segmentation.
E) the anterior-posterior axis.

Answer: E

the anterior-posterior axis

32

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 the 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: B

Allolactose binds to the repressor protein

33

The earliest developmental stage among these choices is
A) germ layers.
B) morula.
C) blastopore.
D) gastrulation.
E) invagination.

Answer: B

morula

34

The cancer-causing forms of the Ras protein are involved in which of the following processes?
A) relaying a signal from a growth factor receptor
B) DNA replication
C) DNA repair
D) cell-cell adhesion
E) cell division

Answer: A

relaying a signal from a growth factor receptor

35

In mammals, the nuclei resulting from the union of the sperm and the egg are first truly diploid at the end of the
A) acrosomal reaction.
B) completion of spermatogenesis.
C) initial cleavage.
D) activation of the egg.
E) completion of gastrulation.

Answer: C

initial cleavage

36

As an embryo develops, new cells are produced as the result of
A) differentiation.
B) preformation.
C) cell division.
D) morphogenesis.
E) epigenesis.

Answer: C

cell division

37

The migratory neural crest cells
A) form most of the central nervous system.
B) serve as precursor cells for the notochord.
C) form the spinal cord in the frog.
D) form neural and non-neural structures in the periphery.
E) form the lining of the lungs and of the digestive tract.

Answer: D

form neural and non-neural structures in the periphery

38

Fertilization normally
A) reinstates diploidy.
B) follows gastrulation.
C) is required for parthenogenesis.
D) merges two diploid cells into one haploid cell.
E) precedes ovulation.

Answer: A

reinstates diploidy

39

Mutations in which of the following genes lead to transformations in the identity of entire body parts?
A) morphogens
B) segmentation genes
C) egg-polarity genes
D) homeotic genes
E) inducers

Answer: D

homeotic genes

40

In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP?
A) increase in glucose and increase in cAMP
B) decrease in glucose and increase in cAMP
C) increase in glucose and decrease in cAMP
D) decrease in glucose and increase in repressor
E) decrease in glucose and decrease in repressor

Answer: B

decrease in glucose and increase in cAMP

41

Embryonic lethal mutations result in
A) phenotypes that prevent fertilization.
B) failure to express maternal effect genes.
C) death during pupation.
D) phenotypes that are never born/hatched.
E) homeotic phenotype changes.

Answer: D

phenotypes that are never born/hatched

42

In a newly fertilized egg, the vitelline layer
A) opens the egg's nuclear membrane to allow haploid sperm DNA to enter.
B) hardens to form a protective cover.
C) secretes hormones that enhance steroidogenesis by the ovary.
D) reduces the loss of water from the egg and prevents desiccation.
E) provides most of the nutrients used by the zygote.

Answer: B

hardens to form a protective cover

43

From earliest to latest, the overall sequence of early development proceeds in which of the following sequences?
A) gastrulation → organogenesis → cleavage
B) ovulation → gastrulation → fertilization
C) cleavage → gastrulation → organogenesis
D) gastrulation → blastulation → neurulation
E) preformation → morphogenesis → neurulation

Answer: C

cleavage → gastrulation → organogenesis

44

During fertilization, the acrosomal contents
A) block polyspermy.
B) help propel more sperm toward the egg.
C) digest the protective jelly coat on the surface of the egg.
D) nourish the mitochondria of the sperm.
E) trigger the completion of meiosis by the sperm.

Answer: C

digest the protective jelly coat on the surface of the egg

45

In eukaryotes, general transcription factors
A) are required for the expression of specific protein-encoding genes.
B) bind to other proteins or to a sequence element within the promoter called the TATA box.
C) inhibit RNA polymerase binding to the promoter and begin transcribing.
D) usually lead to a high level of transcription even without additional specific transcription factors.
E) bind to sequences just after the start site of transcription.

Answer: B

bind to other proteins or to a sequence element within the promoter called the TATA box

46

Which of the following correctly displays the sequence of developmental milestones?
A) cleavage → blastula → gastrula → morula
B) cleavage → gastrula → morula → blastula
C) cleavage → morula → blastula → gastrula
D) gastrula → morula → blastula → cleavage
E) morula → cleavage → gastrula → blastula

Answer: C

cleavage → morula → blastula → gastrula

47

Which of the following is used to make complementary DNA (cDNA) from RNA?
A) restriction enzymes
B) gene cloning
C) DNA ligase
D) gel electrophoresis
E) reverse transcriptase

Answer: E

reverse transcriptase

48
card image

The segment of DNA shown in Figure 20.2 has restriction sites I and II, which create restriction fragments A, B, and C. Which of the gels produced by electrophoresis shown below best represents the separation and identity of these fragments? SEE IMAGE FOR FIGURE

Answer: B

49
card image

Which of the three types of viruses shown above would you expect to include glycoproteins?
A) I only
B) II only
C) III only
D) I and II only
E) all three

Answer: D

I and II only

50

As genetic technology makes testing for a wide variety of genotypes possible, which of the following is likely to be an increasingly troublesome issue?
A) use of genotype information to provide positive identification of criminals
B) using technology to identify genes that cause criminal behaviors
C) the need to legislate for the protection of the privacy of genetic information
D) discrimination against certain racial groups because of major genetic differences
E) alteration of human phenotypes to prevent early disease

Answer: C

the need to legislate for the protection of the privacy of genetic information

51

In the figure, when new viruses are being assembled (IV), what mediates the assembly?
A) host cell chaperones
B) assembly proteins coded for by the host nucleus
C) assembly proteins coded for by the viral genes
D) viral RNA intermediates
E) nothing; they self-assemble

Answer: E

nothing; they self-assemble

52

The first cloned cat, called Carbon Copy, was a calico, but she looked significantly different from her female parent. Why?
A) The environment, as well as genetics, affects phenotypic variation.
B) Fur color genes in cats are influenced by differential acetylation patterns.
C) Cloned animals have been found to have a higher frequency of transposon activation
D) X inactivation in the embryo is random and produces different patterns.
E) The telomeres of the parent's chromosomes were shorter than those of an embryo.

Answer: D

X inactivation in the embryo is random and produces different patterns.

53

The DNA fragments making up a genomic library are generally contained in
A) BACs.
B) recombinant viral RNA.
C) individual wells.
D) DNA-RNA hybrids.
E) radioactive eukaryotic cells.

Answer: A

BACs.

54

What is the most logical sequence of steps for splicing foreign DNA into a plasmid and inserting the plasmid into a bacterium?

I. Transform bacteria with a recombinant DNA molecule.
II. Cut the plasmid DNA using restriction enzymes.
III. Extract plasmid DNA from bacterial cells.
IV. Hydrogen-bond the plasmid DNA to nonplasmid DNA fragments.
V. Use ligase to seal plasmid DNA to nonplasmid DNA.

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

Answer: C

III, II, IV, V, I

55

To introduce a particular piece of DNA into an animal cell, such as that of a mouse, you would find more probable success with which of the following methods?
A) the shotgun approach
B) electroporation followed by recombination
C) introducing a plasmid into the cell
D) infecting the mouse cell with a Ti plasmid
E) transcription and translation

Answer: B

electroporation followed by recombination

56

Which of the following is characteristic of the lytic cycle?
A) Many bacterial cells containing viral DNA are produced.
B) Viral DNA is incorporated into the host genome.
C) The viral genome replicates without destroying the host.
D) A large number of phages are released at a time.
E) The virus-host relationship usually lasts for generations.

Answer: D

A large number of phages are released at a time.

57

How does a bacterial cell protect its own DNA from restriction enzymes?
A) by adding methyl groups to adenines and cytosines
B) by using DNA ligase to seal the bacterial DNA into a closed circle
C) by adding histones to protect the double-stranded DNA
D) by forming "sticky ends" of bacterial DNA to prevent the enzyme from attaching
E) by reinforcing the bacterial DNA structure with covalent phosphodiester bonds

Answer: A

by adding methyl groups to adenines and cytosines

58

Which of the following is least associated with the others?
A) horizontal gene transfer
B) genetic recombination
C) conjugation
D) transformation
E) binary fission

Answer: E

binary fission

59

The reason for using Taq polymerase for PCR is that
A) it is heat stable and can withstand the temperature changes of the cycler.
B) only minute amounts are needed for each cycle of PCR.
C) it binds more readily than other polymerases to primer.
D) it has regions that are complementary to primers.
E) All of these are correct.

Answer: A

it is heat stable and can withstand the temperature changes of the cycler.

60

DNA microarrays have made a huge impact on genomic studies because they
A) can be used to eliminate the function of any gene in the genome.
B) can be used to introduce entire genomes into bacterial cells.
C) allow the expression of many or even all of the genes in the genome to be compared at once.
D) allow physical maps of the genome to be assembled in a very short time.
E) dramatically enhance the efficiency of restriction enzymes.

Answer: C

allow the expression of many or even all of the genes in the genome to be compared at once.

61

Viral genomes vary greatly in size and may include from four genes to several hundred genes. Which of the following viral features is most apt to correlate with the size of the genome?
A) size of the viral capsomeres
B) RNA versus DNA genome
C) double- versus single-strand genomes
D) size and shape of the capsid
E) glycoproteins of the envelope

Answer: D

size and shape of the capsid

62

Why might a laboratory be using dideoxy nucleotides?
A) to separate DNA fragments
B) to clone the breakpoints of cut DNA
C) to produce cDNA from mRNA
D) to sequence a DNA fragment
E) to visualize DNA expression

Answer: D

to sequence a DNA fragment

63
card image

Which enzyme was used to produce the molecule in Figure 20.1?
A) ligase
B) transcriptase
C) a restriction enzyme
D) RNA polymerase
E) DNA polymerase

Answer: C

a restriction enzyme

64

Which of the following statements describes the lysogenic cycle of lambda (λ) phage?
A) After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.
B) Most of the prophage genes are activated by the product of a particular prophage gene.
C) The phage genome replicates along with the host genome.
D) Certain environmental triggers can cause the phage to exit the host genome, switching from the lytic to the lysogenic.
E) The phage DNA is incorporated by crossing over into any nonspecific site on the host cell's DNA.

Answer: C

The phage genome replicates along with the host genome.

65

Which of the following describes the transfer of polypeptide sequences to a membrane to analyze gene expression?
A) Southern blotting
B) Northern blotting
C) Western blotting
D) Eastern blotting
E) RT-PCR

Answer: C

Western blotting

66

Why do RNA viruses appear to have higher rates of mutation?
A) RNA nucleotides are more unstable than DNA nucleotides.
B) Replication of their genomes does not involve proofreading.
C) RNA viruses replicate faster.
D) RNA viruses can incorporate a variety of nonstandard bases.
E) RNA viruses are more sensitive to mutagens.

Answer: B

Replication of their genomes does not involve proofreading.

67

Why is it so important to be able to amplify DNA fragments when studying genes?
A) DNA fragments are too small to use individually.
B) A gene may represent only a millionth of the cell's DNA.
C) Restriction enzymes cut DNA into fragments that are too small.
D) A clone requires multiple copies of each gene per clone.
E) It is important to have multiple copies of DNA in the case of laboratory error.

Answer: B

A gene may represent only a millionth of the cell's DNA

68

Which of these statements about prokaryotes is correct?
A) Bacterial cells conjugate to mutually exchange genetic material.
B) Their genetic material is confined within vesicles known as plasmids.
C) They divide by binary fission, without mitosis or meiosis.
D) The persistence of bacteria throughout evolutionary time is due to their genetic homogeneity (in other words, sameness).
E) Genetic variation in bacteria is not known to occur, because of their asexual mode of reproduction.

Answer: C

They divide by binary fission, without mitosis or meiosis.

69

Which of the following accounts for someone who has had a herpesvirus-mediated cold sore or genital sore getting flare-ups for the rest of his or her life?
A) re-infection by a closely related herpesvirus of a different strain
B) re-infection by the same herpesvirus strain
C) co-infection with an unrelated virus that causes the same symptoms
D) copies of the herpesvirus genome permanently maintained in host nuclei
E) copies of the herpesvirus genome permanently maintained in host cell cytoplasm

Answer: D

copies of the herpesvirus genome permanently maintained in host nuclei

70

Most human-infecting viruses are maintained in the human population only. However, a zoonosis is a disease that is transmitted from other vertebrates to humans, at least sporadically, without requiring viral mutation. Which of the following is the best example of a zoonosis?
A) rabies
B) herpesvirus
C) smallpox
D) HIV
E) hepatitis virus

Answer: A

rabies

71
card image

Which of the three types of viruses shown above would you expect to include a capsid(s)?
A) I only
B) II only
C) III only
D) I and II only
E) all three

Answer: E

all three

72

Which of the following is true of embryonic stem cells but not of adult stem cells?
A) They can differentiate into many cell types.
B) They make up the majority of cells of the tissue from which they are derived.
C) They can continue to replicate for an indefinite period.
D) They can provide enormous amounts of information about the process of gene regulation.
E) One aim of using them is to provide cells for repair of diseased tissue.

Answer: B

They make up the majority of cells of the tissue from which they are derived

73

Which of the following best describes the complete sequence of steps occurring during every cycle of PCR?

1. The primers hybridize to the target DNA.
2. The mixture is heated to a high temperature to denature the double-stranded target DNA.
3. Fresh DNA polymerase is added.
4. DNA polymerase extends the primers to make a copy of the target DNA.

A) 2, 1, 4
B) 1, 3, 2, 4
C) 3, 4, 1, 2
D) 3, 4, 2
E) 2, 3, 4

Answer: A

74

A student wishes to clone a sequence of DNA of ~200 kb. Which vector would be appropriate?
A) a plasmid
B) a typical bacteriophage
C) a BAC
D) a plant virus
E) a large polypeptide

Answer: C

a BAC

75

Genetically engineered plants
A) are more difficult to engineer than animals.
B) include a transgenic rice plant that can help prevent vitamin A deficiency.
C) are being rapidly developed, but traditional plant breeding programs are still the only method used to develop new plants.
D) are able to fix nitrogen themselves.
E) are banned throughout the world.

Answer: B

include a transgenic rice plant that can help prevent vitamin A deficiency.

76

In a hypothetical situation, the genes for sex pilus construction and for tetracycline resistance are located together on the same plasmid within a particular bacterium. If this bacterium readily performs conjugation involving a copy of this plasmid, then the result should be
A) a bacterium that has undergone transduction.
B) the rapid spread of tetracycline resistance to other bacteria in that habitat.
C) the subsequent loss of tetracycline resistance from this bacterium.
D) the production of endospores among the bacterium's progeny.
E) the temporary possession by this bacterium of a completely diploid genome.

Answer: B

the rapid spread of tetracycline resistance to other bacteria in that habitat.

77

In 1997, Dolly the sheep was cloned. Which of the following processes was used?
A) use of mitochondrial DNA from adult female cells of another ewe
B) replication and dedifferentiation of adult stem cells from sheep bone marrow
C) separation of an early stage sheep blastula into separate cells, one of which was incubated in a surrogate ewe
D) fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a surrogate
E) isolation of stem cells from a lamb embryo and production of a zygote equivalent

Answer: D

fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a surrogate

78

The host range of a virus is determined by
A) the enzymes carried by the virus.
B) whether its nucleic acid is DNA or RNA.
C) the proteins in the host's cytoplasm.
D) the enzymes produced by the virus before it infects the cell.
E) the proteins on its surface and that of the host.

Answer: E

the proteins on its surface and that of the host

79

In Fred Griffith's experiments, harmless R strain pneumococcus became lethal S strain pneumococcus as the result of which of the following?
1. horizontal gene transfer
2. transduction
3. conjugation
4. transformation
5. genetic recombination

A) 2 only
B) 4 only
C) 2 and 5
D) 1, 3, and 5
E) 1,4,and 5

Answer: E

1,4,and 5

80

Yeast artificial chromosomes contain which of the following elements?
A) centromeres only
B) telomeres only
C) origin of replication only
D) centromeres and telomeres only
E) centromeres, telomeres, and an origin of replication

Answer: E

centromeres, telomeres, and an origin of replication

81

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

Answer: C

genetic material composed of nucleic acid

82

Emerging viruses arise by
A) mutation of existing viruses.
B) the spread of existing viruses to new host species.
C) the spread of existing viruses more widely within their host species.
D) mutation of existing viruses, the spread of existing viruses to new host species, and the spread of existing viruses more widely within their host species.
E) none of these.

Answer: D

mutation of existing viruses, the spread of existing viruses to new host species, and the spread of existing viruses more widely within their host species.

83

Emerging viruses arise by
A) mutation of existing viruses.
B) the spread of existing viruses to new host species.
C) the spread of existing viruses more widely within their host species.

D) All of the above

Answer D

All of the above

84

To cause a human pandemic, the H5N1 avian flu virus would have to
A) spread to primates such as chimpanzees.
B) develop into a virus with a different host range.
C) become capable of human-to-human transmission.
D) arise independently in chickens in North and South America.
E) become much more pathogenic.

Answer: C

become capable of human-to-human transmission.

85

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) a mixture of the DNA and proteins of both phages.
D) T4 protein and T4 DNA.
E) T4 protein and T2 DNA.

Answer: D

T4 protein and T4 DNA

86

RNA viruses require their own supply of certain enzymes because
A) host cells rapidly destroy the viruses.
B) host cells lack enzymes that can replicate the viral genome.
C) these enzymes translate viral mRNA into proteins.
D) these enzymes penetrate host cell membranes.
E) these enzymes cannot be made in host cells.

Answer: B

host cells lack enzymes that can replicate the viral genome

87

In recombinant DNA methods, the term vector can refer to
A) the enzyme that cuts DNA into restriction fragments.
B) the sticky end of a DNA fragment.
C) a SNP marker.
D) a plasmid used to transfer DNA into a living cell.
E) a DNA probe used to identify a particular gene.

Answer: D

a plasmid used to transfer DNA into a living cell

88

Which of the following tools of recombinant DNA technology is incorrectly paired with its use?
A) restriction enzymeanalysis of RFLPs
B) DNA ligasecutting DNA, creating sticky ends of restriction fragments
C) DNA polymerasepolymerase chain reaction to amplify sections of DNA
D) reverse transcriptaseproduction of cDNA from mRNA
E) electrophoresisseparation of DNA fragments

Answer: B

DNA ligasecutting DNA, creating sticky ends of restriction fragments

89

Plants are more readily manipulated by genetic engineering than are animals because
A) plant genes do not contain introns.
B) more vectors are available for transferring recombinant DNA into plant cells.
C) a somatic plant cell can often give rise to a complete plant.
D) genes can be inserted into plant cells by microinjection.
E) plant cells have larger nuclei.

Answer: C

a somatic plant cell can often give rise to a complete plant.

90

A paleontologist has recovered a bit of tissue from the 400-year-old preserved skin of an extinct dodo (a bird). To compare a specific region of the DNA from the sample with DNA from living birds, which of the following would be most useful for increasing the amount of dodo DNA available for testing?
A) RFLP analysis
B) polymerase chain reaction (PCR)
C) electroporation
D) gel electrophoresis
E) Southern blotting

Answer: B

polymerase chain reaction (PCR)

91

DNA technology has many medical applications. Which of the following is not done routinely at present?
A) production of hormones for treating diabetes and dwarfism
B) production of microbes that can metabolize toxins
C) introduction of genetically engineered genes into human gametes
D) prenatal identification of genetic disease alleles
E) genetic testing for carriers of harmful alleles

Answer: C

introduction of genetically engineered genes into human gametes

92

Which of the following would not be true of cDNA produced using human brain tissue as the starting material?
A) It could be amplified by the polymerase chain reaction.
B) It could be used to create a complete genomic library.
C) It was produced from mRNA using reverse transcriptase.
D) It could be used as a probe to detect genes expressed in the brain.
E) It lacks the introns of the human genes.

Answer: B

It could be used to create a complete genomic library

93

Expression of a cloned eukaryotic gene in a bacterial cell involves many challenges. The use of mRNA and reverse transcriptase is part of a strategy to solve the problem of
A) post-transcriptional processing.
B) electroporation.
C) post-translational processing.
D) nucleic acid hybridization.
E) restriction fragment ligation.

Answer: A

post-transcriptional processing

94

Which of the following sequences in double-stranded DNA is most likely to be recognized as a cutting site for a restriction enzyme?

A) AAGG
TTCC

B) AGTC
TCAG

C) GGCC
CCGG

D) ACCA
TGGT

E) AAAA
TTTT

Answer: C

GGCC,CCGG

95

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then
A) the amino acid inactivates the repressor.
B) the enzymes produced are called inducible enzymes.
C) the repressor is active in the absence of the amino acid.
D) the amino acid acts as a corepressor.
E) the amino acid turns on transcription of the operon.

Answer: D

the amino acid acts as a corepressor

96

Muscle cells differ from nerve cells mainly because they
A) express different genes.
B) contain different genes.
C) use different genetic codes.
D) have unique ribosomes.
E) have different chromosomes.

Answer: A

express different genes

97

The functioning of enhancers is an example of
A) transcriptional control of gene expression.
B) a post-transcriptional mechanism to regulate mRNA.
C) the stimulation of translation by initiation factors.
D) post-translational control that activates certain proteins.
E) a eukaryotic equivalent of prokaryotic promoter functioning.

Answer: A

transcriptional control of gene expression

98

Cell differentiation always involves
A) the production of tissue-specific proteins, such as muscle actin.
B) the movement of cells.
C) the transcription of the myoD gene.
D) the selective loss of certain genes from the genome.
E) the cell's sensitivity to environmental cues, such as light or heat.

Answer: A

the production of tissue-specific proteins, such as muscle actin

99

Which of the following is an example of post-transcriptional control of gene expression?
A) the addition of methyl groups to cytosine bases of DNA
B) the binding of transcription factors to a promoter
C) the removal of introns and alternative splicing of exons
D) gene amplification contributing to cancer
E) the folding of DNA to form heterochromatin

Answer: C

the removal of introns and alternative splicing of exons

100

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?
A) irreversible binding of the repressor to the promoter
B) reduced transcription of the operon's genes
C) buildup of a substrate for the pathway controlled by the operon
D) continuous transcription of the operon's genes
E) overproduction of catabolite activator protein (CAP)

Answer: D

continuous transcription of the operon's genes

101

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene
A) is transcribed in the early embryo.
B) normally leads to formation of tail structures.
C) normally leads to formation of head structures.
D) is a protein present in all head structures.
E) leads to programmed cell death.

Answer: C

normally leads to formation of head structures

102

Which of the following statements about the DNA in one of your brain cells is true?
A) Most of the DNA codes for protein.
B) The majority of genes are likely to be transcribed.
C) Each gene lies immediately adjacent to an enhancer.
D) Many genes are grouped into operon-like clusters.
E) It is the same as the DNA in one of your heart cells.

Answer: E

It is the same as the DNA in one of your heart cells

103

Within a cell, the amount of protein made using a given mRNA molecule depends partly on
A) the degree of DNA methylation.
B) the rate at which the mRNA is degraded.
C) the presence of certain transcription factors.
D) the number of introns present in the mRNA.
E) the types of ribosomes present in the cytoplasm.

Answer: B

the rate at which the mRNA is degraded

104

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?
A) Proto-oncogenes first arose from viral infections.
B) Proto-oncogenes normally help regulate cell division.
C) Proto-oncogenes are genetic "junk."
D) Proto-oncogenes are mutant versions of normal genes.
E) Cells produce proto-oncogenes as they age.

Answer: B

Proto-oncogenes normally help regulate cell division.

105

Genetic variation in bacterial populations cannot result from
A) transduction.
B) transformation
C) conjugation
D) mutation.
E) meiosis.

Answer: E

meiosis.

106

Photoautotrophs use
A) light as an energy source and CO₂ as a carbon source.
B) light as an energy source and methane as a carbon source.
C) N₂ as an energy source and CO₂ as a carbon source.
D) CO₂ as both an energy source and a carbon source.
E) H₂S as an energy source and CO₂ as a carbon source.

Answer: A

light as an energy source and CO₂ as a carbon source

107

Which of the following statements is not true?
A) Archaea and bacteria have different membrane lipids.
B) Both archaea and bacteria generally lack membrane-enclosed organelles.
C) The cell walls of archaea lack peptidoglycan.
D) Only bacteria have histones associated with DNA.
E) Only some archaea use CO₂ to oxidize H₂, releasing methane.

Answer: D

Only bacteria have histones associated with DNA.

108

Which of the following involves metabolic cooperation among prokaryotic cells?
A) binary fission
B) endospore formation
C) endotoxin release
D) biofilms
E) photoautotrophy

Answer: D

biofilms

109

Bacteria perform each of the following ecological roles. Which role typically does not involve a symbiosis?
A) skin commensalist
B) decomposer
C) aggregates with methane-consuming archaea
D) gut mutualist
E) pathogen

Answer: B

decomposer

110

Plantlike photosynthesis that releases O₂ occurs in
A) cyanobacteria.
B) chlamydias.
C) archaea.
D) actinomycetes.
E) chemoautotrophic bacteria.

Answer: A

cyanobacteria

111

The cortical reaction of sea urchin eggs functions directly in
A) the formation of a fertilization envelope.
B) the production of a fast block to polyspermy.
C) the release of hydrolytic enzymes from the sperm.
D) the generation of an electrical impulse by the egg.
E) the fusion of egg and sperm nuclei.

Answer: A

the formation of a fertilization envelope

112

Which of the following is common to the development of both birds and mammals?
A) holoblastic cleavage
B) epiblast and hypoblast
C) trophoblast
D) yolk plug
E) gray crescent

Answer: B

epiblast and hypoblast

113

The archenteron develops into
A) the mesoderm.
B) the blastocoel.
C) the endoderm.
D) the placenta.
E) the lumen of the digestive tract.

Answer: E

the lumen of the digestive tract.

114

What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?
A) extraembryonic membranes
B) yolk
C) cleavage
D) gastrulation
E) development of the brain from ectoderm

Answer: A

extraembryonic membranes

115

In an egg cell treated with EDTA, a chemical that binds calcium and magnesium ions,
A) the acrosomal reaction would be blocked.
B) the fusion of sperm and egg nuclei would be blocked.
C) the fast block to polyspermy would not occur.
D) the fertilization envelope would not form.
E) the zygote would not contain maternal and paternal chromosomes.

Answer: D

the fertilization envelope would not form

116

In humans, identical twins are possible because
A) cytoplasmic determinants are distributed unevenly in unfertilized eggs.
B) extraembryonic cells interact with the zygote nucleus.
C) convergent extension occurs.
D) early blastomeres can form a complete embryo if isolated.
E) the gray crescent divides the dorsal-ventral axis into new cells.

Answer: D

early blastomeres can form a complete embryo if isolated.

117

Cells transplanted from the neural tube of a frog embryo to the ventral part of another embryo develop into nervous system tissues. This result indicates that the transplanted cells were
A) totipotent.
B) determined.
C) differentiated.
D) mesenchymal.
E) apoptotic.

Answer: B

determined