exam 3 review Flashcards


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1

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

A) 32 B) 8 C) 64 D) 16 E) 4

a

2

The centromere is a region in which
A) the nucleus is located prior to mitosis.
B) new spindle microtubules form at either end.
C) sister chromatids remain attached to one another until anaphase. D) metaphase chromosomes become aligned at the metaphase plate. E) chromosomes are grouped during telophase.

c

3

In eukaryotic cells, chromosomes are composed of DNA
A) and proteins

B) and RNA

C) only

D) protein and RNA

E) and phospholipid

a

4

If the cell whose nuclear material is shown in Figure 12.2 continues toward completion of mitosis, which of the following events would occur NEXT?

A) synthesis of chromatids
B) cell membrane synthesis
C) formation of telophase nuclei D) nuclear envelope breakdown

c

5

Where do the microtubules of the spindle originate during mitosis in animal cells?

A) kinetochore B) centromere C) centriole D) centrosome E) chromatid

d

6

Referring to a plant's sexual life cycle, which of the following terms describes the process that leads directly to the formation of gametes?

A) sporophyte mitosis
B) sporophyte meiosis
C) gametophyte mitosis
D) gametophyte meiosis
E) alternation of generations

c

7

When pairs of homologous chromosomes separate during anaphase I of meiosis, A) recombination is not yet complete. B) the maternal chromosomes all move to the same daughter cell. C) the sister chromatids remain attached to one another. D) the synaptonemal complex is formed during telophase I E) All of these

c

8

For the following questions, match the key event of meiosis with the stages listed below.

I. Prophase I II. Metaphase I III. Anaphase I IV.Telophase I

IV. Prophase II VI. Metaphase II VI. Anaphase I VIII. Telophase II

Tetrads of chromosomes are aligned at the equator of the spindle; alignment determines independent assortment.

A) I B) II C) IV D) VII E) VIII

b

9

For the following questions, match the key event of meiosis with the stages listed below.

I. Prophase I II. Metaphase I III. Anaphase I IV.Telophase I

IV. Prophase II VI. Metaphase II VI. Anaphase I VIII. Telophase II

Synapsis of homologous pairs occurs; crossing over may occur.

A) I B) II C) IV D) VI E) VII

a

10

A tetrad includes which of the following sets of DNA strands?
A) four sets of unique chromosomes
B) two sets of sister chromatids of homologous chromosomes that have synapsed C) two single-stranded chromosomes that have synapsed
D) four sets of sister chromatids
E) eight sets of sister chromatids

b

11

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

A) 4 B) 32 C) 64 D) 8 E) 16

d

12

Two characters that appear in a 9:3:3:1 ratio in the F2 generation should have which of the following properties?

A) Each of the traits is controlled by single genes.
B) Each of the genes controlling the characters has two alleles.
C) Sixteen different phenotypes are possible.
D) Four genes are involved.
E) The genes controlling the characters obey the Mendel’s second law of independent assortment.

e

13

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

A) Metaphase I of meiosis

B) Prophase I of meiosis

C) Prophase II of meiosis

D) Anaphase of mitosis

E) Anaphase I of meiosis

e

14

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt × BBtt will have black fur and long tails?

A) 3/16 B) 9/16 C) 3/8 D) 1/2 E) 1/16

d

15

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color. A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?

A) ttrr–dwarf and white B) ttRr–dwarf and pink C) TtRr–tall and red
D) TtRr–tall and pink E) TTRR–tall and red

d

16

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

A) 100% B) 75% C) 25% D) 50% E) 0%

d

17

17) Males are more often affected by sex-linked traits than females because
A) male hormones such as testerone often alter the affects of mutations on the X chromosome.
B) males are hemizygous for the X chromosome.
C) X chromosomes in males generally have more mutations than X chromosomes in females.
D) female hormones such as estrogen often compensate for the effects of mutations on the X chromosome. E) mutations on the Y chromosome often worsen the effects of X-linked mutations.

b

18

18) Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

A) Xn Xn and XN Y

B) XN Xn and XNY

C) Xn Xn and XnY

D) XNXN and XnY

E) XNXN and XNY

b

19

19) Normally, only female cats have the tortoiseshell phenotype because
A) the males die during embryonic development.
B) a male inherits only one allele of the X-linked gene controlling hair color.
C) the Y chromosome has a gene blocking orange coloration.
D) multiple crossovers on the Y chromosome prevent orange pigment production. E) only males can have Barr bodies.

b

20

20) Which of the following statements is true of linkage?
A) All of the traits that Mendel studied; seed color, pod shape, flower color, and others, are due to genes linked on the same chromosome.

B) Crossing over occurs during prophase II of meiosis.

C) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

D) Linked genes are found on different chromosomes.

E) The observed frequency of recombination of two genes that are far apart from each other has a maximum value of100%.

c

21

21) Which of the following investigators was (were) responsible for the following discovery?
In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

A) Frederick Griffith
B) Matthew Meselson and Franklin Stahl
C) Oswald Avery, Maclyn McCarty, and Colin MacLeod D) Alfred Hershey and Martha Chase
E) Erwin Chargaff

e

22

22) Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

A) 16% B) 31% C) 8% D) 42% E) It cannot be determined from the information provided.

c

23

23) What is meant by the description "antiparallel" regarding the strands that make up DNA?
A) One strand contains only purines and the other contains only pyrimidines.
B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. C) Base pairings create unequal spacing between the two DNA strands.
D) The twisting nature of DNA creates nonparallel strands.
E) One strand is positively charged and the other is negatively charged.

b

24

24) 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 prime sequence?

A) 5' A C G U U A G G 3'

B) 5' G C C T A G G 3'

C) 5' A C G T T A G G 3'

D) 3' G C C T A G G 5'

E) 5' G C C U A G G

a

25

The centromere is a region in which

A) chromatids remain attached to one another until anaphase. 
B) metaphase chromosomes become aligned at the metaphase plate. C) chromosomes are grouped during telophase.
 D) the nucleus is located prior to mitosis. 
 E) new spindle microtubules form at either end.

a

26

What is a chromatid?

A) a chromosome in G1 of the cell cycle

B) a replicate chromosome

C) a chromosome found outside the nucleus

D) a special region that holds two centromeres together

E) another name for the chromosomes found in genetics

b

27

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

A) 4 B) 8 C) 16 
D) 32 E) 64

d

28

If there are 20 chromatids in a cell, how many centromeres are there?

A) 10 
B) 20 C) 30 D) 40 E) 80

a

29

For a newly evolving protist, what would be the advantage of using eukaryote -like cell division rather than binary fission?

A) Binary fission would not allow for the formation of new organisms.

B) Cell division would allow for the orderly and efficient segregation of multiple linear

C) Cell division would be faster than binary fission.

D) Cell division allows for lower rates of error per chromosome replication.

E) Binary fission would not allow the organism to have complex cells.

b

30

How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?

A) The daughter cells have half the amount of cytoplasm and half the amount of DNA.

B) The daughter cells have half the number of chromosomes and half the amount of

C) The daughter cells have the same number of chromosomes and half the amount of

D) The daughter cells have the same number of chromosomes and the same amount of

E) The daughter cells have the same number of chromosomes and twice the amount of

d

31

9) Which term describes two centrosomes arranged at opposite poles of the cell?

A) telophase 
B) anaphase
C) prometaphase D) metaphase 
E) prophase

c

32

Which term describes centrioles beginning to move apart in animal cells?

A) telophase 
B) anaphase
C) prometaphase D) metaphase 
E) prophase

e

33

Which is the longest of the mitotic stages?

A) telophase 
B) anaphase
C) prometaphase D) metaphase 
E) prophase

d

34

Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?

A) telophase B) anaphase 
C) prometaphase D) metaphase 
E) prophase

b

35

If cells in the process of dividing are subjected to colchicine, a drug that interferes with the functioning of the spindle apparatus, at which stage will mitosis be arrested?

A) anaphase B) prophase C) telophase 
D) metaphase E) interphase

d

36

A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei each containing how many chromosomes?

A) 12 B) 16 C) 23 D) 46 E) 92

d

37

If there are 20 chromatids in a cell at metaphase, how many chromosomes are there in each daughter cell following cytokinesis?

A) 10 B) 20 C) 30 D) 40 E) 80

a

38

Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that

A) gamma contains more DNA than beta.

B) beta and gamma contain the same amount of DNA.

C) beta contains more RNA than gamma.

D) gamma contains 48 times more DNA and RNA than beta.

E) beta is a plant cell and gamma is an animal cell.

a

39

The best conclusion concerning delta is that the cells

A) contain no DNA.

B) contain no RNA.

C) contain only one chromosome that is very short.

D) are actually in the G0 phase.

E) divide in the G1 phase.

d

40

Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?

A) centromere B) centrosome 
C) centriole D) chromatid 
E) kinetochore

b

41

If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase? 
A) 1 B) 2 C) 4 D) 8 
E) 16

e

42

Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with

A) a single large nucleus.

B) high concentrations of actin and myosin.

C) two abnormally small nuclei.

D) two nuclei.

E) two nuclei but with half the amount of DNA.

d

43

Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants

A) the spindles contain microfibrils in addition to microtubules, whereas animal spindles do not contain microfibrils.

B) sister chromatids are identical, but they differ from one another in animals.

C) a cell plate begins to form at telophase, whereas in animals a cleavage furrow is 
initiated at that stage.

D) chromosomes become attached to the spindle at prophase, whereas in animals 
chromosomes do not become attached until anaphase.

E) spindle poles contain centrioles, whereas spindle poles in animals do not.

c

44

The formation of a cell plate is beginning across the middle of a cell and nuclei are re-forming at opposite ends of the cell. What kind of cell is this?

A) an animal cell in metaphase

B) an animal cell in telophase

C) an animal cell undergoing cytokinesis

D) a plant cell in metaphase

E) a plant cell undergoing cytokinesis

e

45

taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, taxol must affect

A) the fibers of the mitotic spindle.

B) anaphase.

C) formation of the centrioles.

D) chromatid assembly.

E) the S phase of the cell cycle

a

46

In a nucleosome, the DNA is wrapped around

A) polymerase molecules.

B) ribosomes.

C) histones.

D) a thymine dimer.

E) satellite DNA

c

47

The spontaneous loss of amino groups from adenine results in hypoxanthine, an uncommon base, opposite thymine in DNA. What combination of molecules could repair such damage?

A) nuclease, DNA polymerase, DNA ligase

B) telomerase, primase, DNA polymerase

C) telomerase, helicase, single-strand binding protein

D) DNA ligase, replication fork proteins, adenylyl cyclase

E) nuclease, telomerase, primas

a

48

the elongation of the leading strand during DNA synthesis

A) progresses away from the replication fork.

B) occurs in the 3ʹ 5ʹ direction.

C) produces Okazaki fragments.

D) depends on the action of DNA polymerase.

E) does not require a template strand

d

49

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

b

50

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

A) The origins of replication occur only at the 5ʹ end.

B) Helicases and single-strand binding proteins work at the 5ʹ end.

C) DNA polymerase can join new nucleotides only to the 3ʹ end of a growing strand.

D) DNA ligase works only in the 3ʹ 5ʹ direction.

E) Polymerase can work on only one strand at a time

c

51

A biochemist isolates and purifies various molecules needed for DNA replication. When she adds some DNA, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

A) DNA polymerase

B) DNA ligase

C) nucleotides

D) Okazaki fragments

E) primase

b

52

Which of the following statements is true of chromatin?

A) Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and

B) Both heterochromatin and euchromatin are found in the cytoplasm.

C) Heterochromatin is highly condensed, whereas euchromatin is less compact.

D) Euchromatin is not transcribed, whereas heterochromatin is transcribed.

E) Only euchromatin is visible under the light microscope.

c

53

In his work with pneumonia-causing bacteria and mice, Griffith found that

A) the protein coat from pathogenic cells was able to transform nonpathogenic cells.

B) heat-killed pathogenic cells caused pneumonia.

C) some substance from pathogenic cells was transferred to nonpathogenic cells, making 
them pathogenic.

D) the polysaccharide coat of bacteria caused pneumonia.

E) bacteriophages injected DNA into bacteria.

c

54

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

d

55

Which of the following statements describes the eukaryotic chromosome?

A) It is composed of DNA alone.

B) The nucleosome is its most basic functional subunit.

C) The number of genes on each chromosome is different in different cell types of an

D) It consists of a single linear molecule of double-stranded DNA.

E) Active transcription occurs on heterochromatin.

d

56

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

A) There would be an increase in the amount of ʺsatelliteʺ DNA produced during centrifugation.

B) The cellʹs DNA couldnʹt be packed into its nucleus.

C) Spindle fibers would not form during prophase.

D) Amplification of other genes would compensate for the lack of histones.

E) Pseudogenes would be transcribed to compensate for the decreased protein in the cell.

b

57

Which of the following represents the order of increasingly higher levels of organization of chromatin?

A) nucleosome, 30-nm chromatin fiber, looped domain

B) looped domain, 30-nm chromatin fiber, nucleosome

C) looped domain, nucleosome, 30-nm chromatin fiber

D) nucleosome, looped domain, 30-nm chromatin fiber

E) 30-nm chromatin fiber, nucleosome, looped domain

a

58

Which of the following statements describes histones?

A) Each nucleosome consists of two molecules of histone H1.

B) Histone H1 is not present in the nucleosome bead; instead it is involved in the formation of higher-level chromatin structures.

C) The carboxyl end of each histone extends outward from the nucleosome and is called a ʺhistone tail.ʺ

D) Histones are found in mammals, but not in other animals or in plants.

E) The mass of histone in chromatin is approximately nine times the mass of DNA.

b

59

Why do histones bind tightly to DNA?

A) Histones are positively charged, and DNA is negatively charged.

B) Histones are negatively charged, and DNA is positively charged.

C) Both histones and DNA are strongly hydrophobic.

D) Histones are covalently linked to the DNA.

E) Histones are highly hydrophobic, and DNA is hydrophilic.

a

60

In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?

A) DNA without attached histones

B) DNA with H1 only

C) the 10 nm chromatin fiber

D) the 30 nm chromatin fiber

E) the metaphase chromosome

d

61

Which of the following are primarily responsible for cytokinesis in plant cells?

A) kinetochores

B) Golgi-derived vesicles

C) actin and myosin

D) centrioles and basal bodies

E) cyclin-dependent kinases

b

62

Chromosomes first become visible during which phase of mitosis?

A) prometaphase 
B) telophase C) prophase D) metaphase 
E) anaphase

c

63

During which phases of mitosis are chromosomes composed of two chromatids?

A) from interphase through anaphase 
B) from G1 of interphase through metaphase 
C) from metaphase through telophase D) from anaphase through telophase 
E) from G2 of interphase through metaphase

e

64

In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?

A) seedless plants B) dinoflagellates 
C) diatoms
D) B and C only 
E) A, B, and C

d

65

Movement of the chromosomes during anaphase would be most affected by a drug that

A) reduces cyclin concentrations. 
B) increases cyclin concentrations.
C) prevents elongation of microtubules. D) prevents shortening of microtubules. 
E) prevents attachment of the microtubules to the kinetochore

d

66

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle was the nucleus with 6 picograms of DNA?

A) G0 B) G1 
C) S D) G2 
E) M

d

67

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. Those cells would have __________ picograms at the end of the S phase and __________ picograms at the end of G 2.

A) 8; 8 B) 8; 16 C) 16; 8 
D) 16; 16 E) 12; 16

d

68

The somatic cells derived from a single-celled zygote divide by which process? A) meiosis 
B) mitosis
C) replication 
D) cytokinesis alone 
E) binary fission

b

69

Imagine looking through a microscope at a squashed onion root tip. The chromosomes of many of the cells are plainly visible. In some cells, replicated chromosomes are aligned along the center (equator) of the cell. These particular cells are in which stage of mitosis?

A) telophase B) prophase C) anaphase 
D) metaphase
E) prometaphase

d

70

In order for anaphase to begin, which of the following must occur?

A) Chromatids must lose their kinetochores. 
B) Cohesin must attach the sister chromatids to each other. C) Cohesin must be cleaved enzymatically.
D) Kinetochores must attach to the metaphase plate. 
E) Spindle microtubules must begin to depolymerize

c

71

Why do chromosomes coil during mitosis?

A) to increase their potential energy

B) to allow the chromosomes to move without becoming entangled and breaking

C) to allow the chromosomes to fit within the nuclear envelope

D) to allow the sister chromatids to remain attached

E) to provide for the structure of the centromere

b

72

These Protists are intermediate in what sense?

A) They reproduce by binary fission in their early stages of development and by mitosis 
when they are mature.

B) They never coil up their chromosomes when they are dividing.

C) They use mitotic division but only have circular chromosomes.

D) They maintain a nuclear envelope during division.

E) None of them form spindles

d

73

Which of the following is a function of those spindle microtubules that do not attach to kinetochores?

A) maintaining an appropriate spacing among the moving chromosomes

B) producing a cleavage furrow when telophase is complete

C) providing the ATP needed by the fibers attached to kinetochores

D) maintaining the region of overlap of fibers in the cellʹs center

E) pulling the poles of the spindles closer to one another

d

74

Which of the following happens at the conclusion of meiosis I?

A) Homologous chromosomes are separated. 
B) The chromosome number per cell is conserved. C) Sister chromatids are separated.
D) Four daughter cells are formed. 
E) The sperm cells elongate to form a head and a tail end

a

75

If an organism is diploid and a certain gene found in the organism has 18 known alleles (variants), then any given organism of that species can/must have which of the following?

A) At most, 2 alleles for that gene
B) Up to 18 chromosomes with that gene 
C) Up to 18 genes for that trait
D) A haploid number of 9 chromosomes 
E) Up to, but not more than, 18 different traits

a

76

A certain femaleʹs chromosomes 12 both have the blue gene and chromosomes 19 both have the long gene. As cells in her ovaries undergo meiosis, her resulting eggs (ova) may have which of the following?

A) Either two chromosomes 12 with blue genes or two with orange genes B) Either two chromosomes 19 with long genes or two with short genes 
C) Either one blue or one orange gene in addition to either one long and one short gene D) One chromosome 12 with one blue gene and one chromosome 19 with one long gene

d

77

A human cell containing 22 autosomes and a Y chromosome is

A) a sperm. 
B) an egg.
C) a zygote.
D) a somatic cell of a male. 
E) a somatic cell of a female

a

78

Which life cycle stage is found in plants but not animals?

A) Gamete 
B) Zygote
 C) Multicellular diploid D) Multicellular haploid 
E) Unicellular diploid

d

79

Homologous chromosomes move toward opposite poles of a dividing cell during A) mitosis. 
B) meiosis I. C) meiosis II. D) fertilization. 
E) binary fission

b

80

Meiosis II is similar to mitosis in that

A) sister chromatids separate during anaphase. 
B) DNA replicates before the division. C) the daughter cells are diploid.
D) homologous chromosomes synapse. 
E) the chromosome number is reduced

a

81

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA 
content of the same cell at metaphase of meiosis I would be

A) 0.25x. 
B) 0.5x. C) x. D) 2x. 
E) 4x

d

82

If we continued to follow the cell lineage from question 5, then the DNA content of a single cell at metaphase of meiosis II would be

A) 0.25x. B) 0.5x. 
C) x. D) 2x. E) 4x

c

83

Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?

A) The chromosomes are ʺreeled inʺ by the contraction of spindle microtubules.

B) Motor proteins of the kinetochores move the chromosomes along the spindle

C) Non-kinetochore spindle fibers serve to push chromosomes in the direction of the

D) both A and B

E) A, B, and C

b

84

What is the most probable hypothesis about these intermediate forms of cell division?

A) They represent a form of cell reproduction which must have evolved completely 
separately from those of other organisms.

B) They demonstrate that these species are not closely related to any of the other Protists 
and may well be a different Kingdom.

C) They rely on totally different proteins for the processes they undergo.

D) They may be more closely related to plant forms that also have unusual mitosis.

E) They show some of the evolutionary steps toward complete mitosis but not all.

e

85

How many different combinations of maternal and paternal chromosomes can be packaged in gametes made by an organism with a diploid number of 8 (2n = 8)?

A) 2 B) 4 C) 8 
D) 16 E) 32

d

86

In prophase I of meiosis in female Drosophila, studies have shown that there is phosphorylation of an amino acid in the tails of histones. A mutation in flies that interferes with this process results in sterility. Which of the following is the most likely hypothesis?

A) These oocytes have no histones.
B) Any mutation during oogenesis results in sterility. 
C) Phosphorylation of all proteins in the cell must result.
D) Histone tail phosphorylation prohibits chromosome condensation. 
E) Histone tails must be removed from the rest of the histones

d

87

About how many more genes are there in the haploid human genome than in a typical bacterial genome?

A) 10 X B) 100 X 
C) 1000 X D) 10,000 X 
E) 100,000 X

c

88

When DNA is compacted by histones into 10 nm and 30 nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?

A) DNA supercoiling at or around H1
B) methylation and phosphorylation of histone tails 
C) hydrolysis of DNA molecules where they are wrapped around the nucleosome core D) accessibility of heterochromatin to phosphorylating enzymes 
E) nucleotide excision and reconstruction

b

89

Studies of nucleosomes have shown that histones (except H1) exist in each nucleosome as two kinds of tetramers: one of 2 H2A molecules and 2 H2B molecules, and the other as 2 H3 and 2 H4 molecules. Which of the following is supported by this data?

A) DNA can wind itself around either of the two kinds of tetramers. B) The two types of tetramers associate to form an octamer. 
C) DNA has to associate with individual histones before they form tetramers. D) Only H2A can form associations with DNA molecules. 
E) The structure of H3 and H4 molecules is not basic like that of the other histones.

b

90

A typical bacterial chromosome has ~4.6 million nucleotides. This supports approximately how many genes?

A) 4.6 million B) 4.4 thousand 
C) 45 thousand D) about 400

b

91

Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?

A) double-stranded DNA, 4 kinds of dNTPs, primers, origins B) topoisomerases, telomerase, polymerases 
C) G-C rich regions, polymerases, chromosome nicks D) nucleosome loosening, 4 dNTPs, 4 rNTPs 
E) ligase, primers, nucleases

a

92

Which would you expect of a eukaryotic cell lacking telomerase?

A) a high probability of becoming cancerous 
B) production of Okazaki fragments C) inability to repair thymine dimers D) a reduction in chromosome length 
E) high sensitivity to sunlight

d

93

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells have which impaired ability?

A) They cannot replicate DNA. B) They cannot undergo mitosis. 
C) They cannot exchange DNA with other cells. D) They cannot repair thymine dimers. 
E) They do not recombine homologous chromosomes during meiosis

d

94

Which of the following help to hold the DNA strands apart while they are being replicated?

A) primase 
B) ligase
C) DNA polymerase
D) single-strand binding proteins 
E) exonuclease

d

95

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

A) synthesize RNA nucleotides to make a primer B) catalyze the lengthening of telomeres 
C) join Okazaki fragments together D) unwind the parental double helix 
E) stabilize the unwound parental DNA

c

96

What is the function of topoisomerase?

A) relieving strain in the DNA ahead of the replication fork

B) elongation of new DNA at a replication fork by addition of nucleotides to the existing chain

C) the addition of methyl groups to bases of DNA

D) unwinding of the double helix

E) stabilizing single-stranded DNA at the replication fork

a

97

A new DNA strand elongates only in the 5ʹ to 3ʹ direction because

A) DNA polymerase begins adding nucleotides at the 5ʹ end of the template.

B) Okazaki fragments prevent elongation in the 3ʹ to 5ʹ direction.

C) the polarity of the DNA molecule prevents addition of nucleotides at the 3ʹ end.

D) replication must progress toward the replication fork.

E) DNA polymerase can only add nucleotides to the free 3ʹ end.

e

98

Which of the following best describes the addition of nucleotides to a growing DNA chain?

A) A nucleoside triphosphate is added to the 5ʹ end of the DNA, releasing a molecule of

B) A nucleoside triphosphate is added to the 3ʹ end of the DNA, releasing a molecule of

C) A nucleoside diphosphate is added to the 5ʹ end of the DNA, releasing a molecule of

D) A nucleoside diphosphate is added to the 3ʹ end of the DNA, releasing a molecule of

E) A nucleoside monophosphate is added to the 5ʹ end of the DNA.

b

99

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 3ʹ end of the growing 
strand, and the lagging strand is synthesized by adding nucleotides to the 5ʹ

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.

a

100

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

A) the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

B) the nucleoside triphosphates have two phosphate groups; ATP has three phosphate

C) ATP contains three high-energy bonds; the nucleoside triphosphates have two.

D) ATP is found only in human cells; the nucleoside triphosphates are found in all 
animal and plant cells.

E) triphosphate monomers are active in the nucleoside triphosphates, but not in ATP.

a

101

Which of the following synthesizes short segments of RNA?

A) helicase 
B) DNA polymerase III C) ligase
D) DNA polymerase I 
E) primase

e

102

Which of the following covalently connects segments of DNA?

A) helicase 
B) DNA polymerase III C) ligase
D) DNA polymerase I 
E) primase

c

103

Which of the following separates the DNA strands during replication?

A) helicase 
B) DNA polymerase III C) ligase
D) DNA polymerase I 
E) primase

a

104

Which of the following removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3ʹ end of Okazaki fragments?

A) helicase
 B) DNA polymerase III 
C) ligase
D) DNA polymerase I 
E) primase

d

105

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

A) leading strands and Okazaki fragments. B) lagging strands and Okazaki fragments. 
C) Okazaki fragments and RNA primers. D) leading strands and RNA primers. 
E) RNA primers and mitochondrial DNA.

a

106

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 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

c

107

To repair a thymine dimmer by nucleotide excision repair, in which order do the necessary enzymes act?

A) exonuclease, DNA polymerase III, RNA primase B) helicase, DNA polymerase I, DNA ligase 
C) DNA ligase, nuclease, helicase
D) DNA polymerase I, DNA polymerase III, DNA ligase 
E) endonuclease, DNA polymerase I, DNA ligase

e

108

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

b

109

The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?

A) the inactivity of this DNA
B) the low frequency of mutations occurring in this DNA 
C) that new evolution of telomeres continues
D) that mutations in telomeres are relatively advantageous 
E) that the critical function of telomeres must be maintained

e

110

The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?

A) adding a single 5ʹ cap structure that resists degradation by nucleases

B) causing specific double strand DNA breaks that result in blunt ends on both strands

C) causing linear ends of the newly replicated DNA to circularize

D) adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn

E) adding numerous GC pairs which resist hydrolysis and maintain chromosome integrity

d

111

Eukaryotic telomeres replicate differently than the rest of the chromosome. 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 5ʹ end

C) Gaps left at the 5ʹ end of the lagging strand because of the need for a 3ʹ onto which nucleotides can attach

D) Gaps left at the 3ʹ end of the lagging strand because of the need for a primer

E) The ʺno endsʺ of a circular chromosome

c

112

What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

A) the particular DNA polymerase catalyzing the reaction
 B) the relative amounts of the four nucleoside triphosphates in the cell 
C) the nucleotide sequence of the template strand D) the primase used in the reaction 
E) the arrangement of histones in the sugar phosphate backbone

c

113

Which enzyme catalyzes the elongation of a DNA strand in the 5ʹ 3ʹ direction? A) primase 
B) DNA ligase
C) DNA polymerase III D) topoisomerase 
E) helicase

c

114

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

A) No proofreading will occur.
B) No replication fork will be formed. 
C) The DNA will supercoil.
D) Replication will occur via RNA polymerase alone. 
E) Replication will require a DNA template from another source

b

115

An Okazaki fragment has which of the following arrangements?

A) primase, polymerase, ligase 
B) 3ʹ RNA nucleotides, DNA nucleotides 5ʹ C) 5ʹ RNA nucleotides, DNA nucleotides 3ʹ D) DNA polymerase I, DNA polymerase III 
E) 5ʹ DNA to 3ʹ

c

116

If mammalian cells receive a go-ahead signal at the G1 checkpoint, they will

A) move directly into telophase. B) complete the cycle and divide. 
C) exit the cycle and switch to a nondividing state. D) show a drop in MPF concentration. 
E) complete cytokinesis and form new cell walls.

b

117

Cells that are in a nondividing state are in which phase?

A) G0 
B) G2 
C) G1 
D) S E) M

a

118

What causes the decrease in the amount of cyclin at a specific point in the cell cycle?

A) an increase in production once the restriction point is passed 
B) the cascade of increased production once its protein is phosphorylated by Cdk C) the changing ratio of cytoplasm to genome
D) its destruction by a process initiated by the activity of its complex with a cyclin 
E) the binding of PDGF to receptors on the cell surface

d

119

Which of the following is released by platelets in the vicinity of an injury?

A) PDGF 
B) MPF
C) protein kinase D) cyclin 
E) Cdk

a

120

Which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them?

A) PDGF B) MPF 
C) protein kinase D) cyclin 
E) Cdk

c

121

Fibroblasts have receptors for this substance on their plasma membranes:

A) PDGF 
B) MPF
C) protein kinase D) cyclin 
E) Cdk

a

122

Which of the following is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex?

A) PDGF B) MPF 
C) protein kinase D) cyclin 
E) Cdk

d

123

Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?

A) PDGF B) MPF 
C) protein kinase D) cyclin 
E) Cdk

e

124

Which of the following triggers the cellʹs passage past the G2 checkpoint into mitosis? 
A) PDGF B) MPF 
C) protein kinase D) cyclin 
E) Cdk

b

125

This is the shortest part of the cell cycle: A) G0 
B) G1 
C) S D) G2 
E) M

e

126

DNA is replicated at this time of the cell cycle: A) G0 
B) G1 
C) S D) G2 
E) M

c

127

The ʺrestriction pointʺ occurs here: A) G0 
B) G1 
C) S D) G2 
E) M

b

128

Nerve and muscle cells are in this phase: A) G0 
B) G1 
C) S D) G2 
E) M

a

129

The cyclin component of MPF is destroyed toward the end of this phase: A) G0 
B) G1 
C) S D) G2 
E) M

e

130

An enzyme that attaches a phosphate group to another molecule is called a A) phosphatase. 
B) phosphorylase. C) kinase.
D) cyclase. 
E) ATPase

c

131

Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called 
A) ATPases.
B) kinetochores. 
C) centrioles.
D) proton pumps. 
E) cyclins

e

132

The MPF protein complex turns itself off by
A) activating a process that destroys cyclin component. 
B) activating an enzyme that stimulates cyclin. C) binding to chromatin.
D) exiting the cell. 
E) activating the anaphase-promoting complex.

a

133

A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation? 
A) The cell would prematurely enter anaphase. B) The cell would never leave metaphase.
C) The cell would never enter metaphase. 
D) The cell would never enter prophase.
E) The cell would undergo normal mitosis, but fail to enter the next G1 phase.

e

134

Density-dependent inhibition is explained by which of the following?

A) As cells become more numerous, they begin to squeeze against each other, restricting 
their size and ability to produce control factors.

B) As cells become more numerous, the cell surface proteins of one cell contact the 
adjoining cells and they stop dividing.

C) As cells become more numerous, the protein kinases they produce begin to compete 
with each other, such that the proteins produced by one cell essentially cancel those 
produced by its neighbor.

D) As cells become more numerous, more and more of them enter the S phase of the cell

E) As cells become more numerous, the level of waste products increases, eventually 
slowing down metabolism.

b

135

What is a genome?
A) The complete complement of an organismʹs genes 
B) A specific set of polypeptides within each cell
C) A specialized polymer of four different kinds of monomers
D) A specific segment of DNA that is found within a prokaryotic chromosome 
E) An ordered display of chromosomes arranged from largest to smallest

a

136

Which of the following statements about genes is incorrect?

A) Genes correspond to segments of DNA.

B) Many genes contain the information needed for cells to synthesize enzymes and other proteins.

C) During fertilization, both the sperm and the ovum contribute genes to the resulting fertilized egg.

D) One gene only is used in a specific cell type.

E) Genetic differences can result from changes in the DNA called mutations.

d

137

Asexual reproduction and sexual reproduction differ in all but which of the following ways?

A) Individuals reproducing asexually transmit 100% of their genes to their progeny, whereas individuals reproducing sexually transmit only 50%.

B) Asexual reproduction produces offspring that are genetically identical to the parents, whereas sexual reproduction gives rise to genetically distinct offspring.

C) Asexual reproduction involves a single parent, whereas sexual reproduction involves two.

D) Asexual reproduction requires only mitosis, whereas sexual reproduction always involves meiosis.

E) Asexual reproduction is utilized only by fungi and protists, whereas sexual reproduction is utilized only by plants and animals.

e

138

If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants?

A) Backtrack through her previous experiments to obtain another plant with the same traits.

B) Breed this plant with another plant with much weaker traits.

C) Clone the plant asexually to produce an identical one.

D) Force the plant to self-pollinate to obtain an identical one.

E) Add nitrogen to the soil of the offspring of this plant so the desired traits continue.

c

139

Asexual reproduction results in identical offspring unless which of the following occurs? A) Natural selection 
B) Cloning
C) Crossing over D) Mutation 
E) Environmental change

d

140

In a life cycle such as that shown in part III of Figure 13.1, if the zygoteʹs chromosome number is 10, which of the following will be true? 
A) The sporophyteʹs chromosome number per cell is 10 and the gametophyteʹs is 5. B) The sporophyteʹs chromosome number per cell is 5 and the gametophyteʹs is 10. 
C) The sporophyte and gametophyte each have 10 chromosomes per cell. D) The sporophyte and gametophyte each have 5 chromosomes per cell. 
E) The sporophyte and gametophyte each have 20 chromosomes per cell

a

141

A tetrad includes which of the following sets of DNA strands? A) Two single-stranded chromosomes that have synapsed 
B) Two sets of sister chromatids that have synapsed C) Four sets of sister chromatids
D) Four sets of unique chromosomes 
E) Eight sets of sister chromatids

b

142

Which of the following about the law of segregation is false?

A) It states that each of two alleles for a given trait segregate into different gametes.

B) It can be explained by the segregation of homologous chromosomes during meiosis.

C) It can account for the 3:1 ratio seen in the F2 generation of Mendelʹs crosses.

D) It can be used to predict the likelihood of transmission of certain genetic diseases within families.

E) It is a method that can be used to determine the number of chromosomes in a plant.

e

143

Mendel was able to draw his ideas of segregation and independent assortment because of the influence of which of the following?

A) His reading and discussion of Darwinʹs Origin of Species

B) The understanding of particulate inheritance he learned from renowned scientists of 
his time

C) His discussions of heredity with his colleagues at major universities

D) His reading of the scientific literature current in the field

E) His experiments with the breeding of plants such as peas

e

144

Mendelʹs observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division? 
A) Prophase I of meiosis B) Prophase II of meiosis 
C) Metaphase I of meiosis D) Anaphase I of meiosis 
E) Anaphase of mitosis

d

145

The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?

A) None of the traits obeyed the law of segregation.

B) The diploid number of chromosomes in the pea plants was 7.

C) All of the genes controlling the traits were located on the same chromosome.

D) All of the genes controlling the traits behaved as if they were on different

E) The formation of gametes in plants occurs by mitosis only.

d

146

Mendelʹs second law of independent assortment has its basis in which of the following events of meiosis I? 
A) Synapsis of homologous chromosomes B) Crossing over 
C) Alignment of tetrads at the equator D) Separation of homologs at anaphase 
E) Separation of cells at telophase

c

147

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt × BBtt will have black fur and long tails? 
A) 1/16 B) 3/16 
C) 3/8 D) 1/2 
E) 9/16

d

148

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short? 
A) 1 B) 1/2 
C) 1/4 D) 1/6 
E) 0

b

149

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently. If 1,000 F 2 offspring resulted from the 
cross, approximately how many of them would you expect to have red, terminal flowers? A) 65 
B) 190 C) 250 D) 565 E) 750

b

150

In a cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC? A) 1/4 
B) 1/8 C) 1/16 D) 1/32 E) 1/64

e

151

Given the parents AABBCc × AabbCc, assume simple dominance and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent? 
A) 1/4 B) 1/8 C) 3/4 D) 3/8 
E) 1

c

152

Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies? 
A) yyBB and yyBB B) yyBB and yyBb C) yyBb and yyBb D) yyBB and yybb 
E) yyBb and yybb

c

153

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male? 
A) Tortoiseshell females; tortoiseshell males B) Black females; orange males 
C) Orange females; orange males
D) Tortoiseshell females; black males 
E) Orange females; black males

d

154

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents? 
A) XcXc and XcY B) XcXc and XCY C) XCXC and XcY 
D) XCXC and XCY E) XCXc and XCY

e

155

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have 
cinnabar eyes? A) 0% 
B) 25% C) 50% D) 75% 
E) 100%

e

156

Calico cats are female because
A) a male inherits only one of the two X-linked genes controlling hair color. 
B) the males die during embryonic development.
C) the Y chromosome has a gene blocking orange coloration. D) only females can have Barr bodies. 
E) multiple crossovers on the Y chromosome prevent orange pigment production

a

157

How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced? 
A) The two genes are linked.
B) The two genes are linked but on different chromosomes. 
C) Recombination did not occur in the cell during meiosis. D) The testcross was improperly performed. 
E) Both of the characters are controlled by more than one gene

a

158

New combinations of linked genes are due to which of the following? A) Nondisjunction 
B) Crossing over
C) Independent assortment D) Mixing of sperm and egg 
E) Deletions

b

159

What does a frequency of recombination of 50% indicate?
A) The two genes are likely to be located on different chromosomes. 
B) All of the offspring have combinations of traits that match one of the two parents. C) The genes are located on sex chromosomes.
D) Abnormal meiosis has occurred. 
E) Independent assortment is hindered

a

160

A 0.1% frequency of recombination is observed A) only in sex chromosomes. 
B) only on genetic maps of viral chromosomes. C) on unlinked chromosomes.
D) in any two genes on different chromosomes. 
E) in genes located very close to one another on the same chromosome

e

161

Abnormal chromosomes are frequent in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse? 
A) An increase in non-disjunction
B) Expression of inappropriate gene products 
C) A decrease in mitotic frequency
D) Death of the cancer cells in the tumor 
E) Sensitivity of the immune system

b

162

Women with Turner syndrome have a genotype characterized as which of the following? A) aabb 
B) Mental retardation and short arms C) A karyotype of 45, X
D) A karyotype of 47, XXX 
E) A deletion of the Y chromosome

c

163

For a couple of decades, biologists knew the nucleus contained DNA and proteins. The prevailing opinion was that the genetic material was proteins, and not DNA. The reason for this belief was that proteins are more complex than DNA. What was the basis of this thinking? 
A) Proteins have a greater variety of three-dimensional forms than does DNA. B) Proteins have two different levels of structural organization; DNA has four. 
C) Proteins are made of 40 amino acids and DNA is made of four nucleotides. D) Some viruses only transmit proteins. 
E) A and B are correct.

a

164

In his transformation experiments, what did Griffith observe?

A) Mutant mice were resistant to bacterial infections.

B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

C) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.

D) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.

E) Mice infected with a pathogenic strain of bacteria can spread the infection to other mice.

b

165

What does transformation involve in bacteria?
A) the creation of a strand of DNA from an RNA molecule 
B) the creation of a strand of RNA from a DNA molecule C) the infection of cells by a phage DNA molecule
D) the type of semiconservative replication shown by DNA 
E) assimilation of external DNA into a cell

e

166

After mixing a heat-killed, phosphorescent strain of bacteria with a living non-phosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait? 
A) DNA passed from the heat-killed strain to the living strain. B) Protein passed from the heat-killed strain to the living strain. 
C) The phosphorescence in the living strain is especially bright. D) Descendants of the living cells are also phosphorescent. 
E) Both DNA and protein passed from the heat-killed strain to the living strain

d

167

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, but protein does not. 
C) DNA contains nitrogen, whereas protein does not.
D) DNA contains purines, whereas protein includes pyrimidines. 
E) RNA includes ribose, while DNA includes deoxyribose sugars

b

168

Chargaffʹs analysis of the relative base composition of DNA was significant because he was able to show that 
A) the relative proportion of each of the four bases differs within individuals of a species. B) the human genome is more complex than that of other species. 
C) the amount of A is always equivalent to T, and C to G.
D) the amount of ribose is always equivalent to deoxyribose. 
E) transformation causes protein to be brought into the cell

c

169

Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA? 
A) the diameter of the helix B) the rate of replication 
C) the sequence of nucleotides
D) the bond angles of the subunits 
E) the frequency of A vs. T nucleotides

a

170

Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions? 
A) Replication is semi-conservative. B) Replication is not dispersive. 
C) Replication is not semi-conservative. D) Replication is not conservative. 
E) Replication is neither dispersive nor conservative

d

171

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing ʺheavyʺ 
nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in Figure 16.1 would be expected after one round of DNA replication in the presence 
of 14N?

d

172

Independent assortment of chromosomes occurs. A) The statement is true for mitosis only. 
B) The statement is true for meiosis I only.
C) The statement is true for meiosis II only.
D) The statement is true for mitosis and meiosis I. 
E) The statement is true for mitosis and meiosis II.

b

173

Chromatids are separated from each other. A) The statement is true for mitosis only. 
B) The statement is true for meiosis I only.
C) The statement is true for meiosis II only.
D) The statement is true for mitosis and meiosis I. 
E) The statement is true for mitosis and meiosis II.

e