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

A) 10

B) 20

C) 30

D) 40

E) 80

A

Which of the following statements is not true?

A) Mitosis produces new nuclei with exactly the same chromosomal endowment as the parent nucleus.

B) Mitosis may occur without cytokinesis.

C) Mitosis and cytokinesis are required for asexual reproduction.

D) All cells come from a preexisting cell.

E) The mitotic spindles in prokaryotic cells are composed of microtubules.

E

The lettered circle in Figure 12.1 shows a diploid nucleus with four chromosomes. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is symbolized as black and the other haploid set is gray. The chromosomes in the unlettered circle have not yet replicated. Choose the correct chromosomal conditions for the following stages.

at prometaphase of mitosis

B

The lettered circle in Figure 12.1 shows a diploid nucleus with four chromosomes. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is symbolized as black and the other haploid set is gray. The chromosomes in the unlettered circle have not yet replicated. Choose the correct chromosomal conditions for the following stages.

one daughter nucleus at telophase of mitosis

E

The questions below refer to the following terms. Each term may be used once, more than once, or not at all.

A. telophase

B. anaphase

C. prometaphase

D. metaphase

E. prophase

Two centrosomes are arranged at opposite poles of the cell.

C

The questions below refer to the following terms. Each term may be used once, more than once, or not at all.

A. telophase

B. anaphase

C. prometaphase

D. metaphase

E. prophase

Centrioles begin to move apart in animal cells.

E

The questions below refer to the following terms. Each term may be used once, more than once, or not at all.

A. telophase

B. anaphase

C. prometaphase

D. metaphase

E. prophase

This is the longest of the mitotic stages.

D

Which of the following does not occur during mitosis?

A) condensation of the chromosomes

B) replication of the DNA

C) separation of sister chromatids

D) spindle formation

E) separation of the centrosomes

B

In some organisms, mitosis occurs without cytokinesis occurring. This will result in

A) cells with more than one nucleus.

B) cells that are unusually small.

C) cells lacking nuclei.

D) destruction of chromosomes.

E) cell cycles lacking an S phase.

A

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell cycle would be most disrupted by cytochalasin B?

A) spindle formation

B) spindle attachment to kinetochores

C) DNA synthesis

D) cell elongation during anaphase

E) cleavage furrow formation

E

A red blood cell (RBC) has a 120-day life span. If an average adult has 5 L of blood, and each microliter (μL) contains 5 million RBCs, how many new cells must be produced each second to replace the entire RBC population? (1 μL = 10-6 L)

A) 30,000

B) 2,400

C) 2,400,000

D) 18,000

E) 30,000,000

C

The decline of MPF activity at the end of mitosis is caused by

A) the destruction of the protein kinase (Cdk).

B) decrease in the synthesis of cyclin.

C) the degradation of cyclin.

D) synthesis of DNA.

E) an increase in the cell's volume-to-genome ratio.

C

One difference between a cancer cell and a normal cell is that

A) the cancer cell is unable to synthesize DNA.

B) the cell cycle of the cancer cell is arrested at the S phase.

C) cancer cells continue to divide even when they are tightly packed together.

D) cancer cells cannot function properly because they suffer from density-dependent inhibition.

E) cancer cells are always in the M phase of the cell cycle.

C

A particular cell has half as much DNA as some of the other cells in a mitotically active tissue. The cell in question is most likely in

A) G1.

B) G2.

C) prophase.

D) metaphase.

E) anaphase.

A

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to

A) disruption of mitotic spindle formation.

B) inhibition of regulatory protein phosphorylation.

C) suppression of cyclin production.

D) myosin denaturation and inhibition of cleavage furrow formation.

E) inhibition of DNA synthesis.

A

Through a microscope, you can see a cell plate beginning to develop across the middle of the cell and nuclei re-forming on either side of the cell plate. The cell is most likely

A) an animal cell in the process of cytokinesis.

B) a plant cell in the process of cytokinesis.

C) an animal cell in the S phase of the cell cycle.

D) a bacterial cell dividing.

E) a plant cell in metaphase.

B

Increases in the enzymatic activity of some protein kinases important for the regulation of the cell cycle are due to

A) kinase synthesis by ribosomes.

B) activation of inactive kinases by binding to cyclins.

C) conversion of inactive cyclins to active kinases by means of phosphorylation.

D) cleavage of the inactive kinase molecules by cytoplasmic proteases.

E) a decline in external growth factors to a concentration below the inhibitory threshold.

B

Which of these is not a carcinogen?

A) testosterone

B) cigarette smoke

C) UV light

D) fat

E) All of the above are carcinogens.

E

During prophase, a homologous pair of chromosomes consists of

A) four chromosomes and two chromatids.

B) two chromosomes and two chromatids.

C) two chromosomes and four chromatids.

D) one chromosome and two chromatids.

E) one chromosome and four chromatids.

C

Spindle fibers attach to kinetochores during

A) metaphase.

B) prometaphase.

C) interphase.

D) anaphase.

E) telophase.

B

Chromosomes become visible during

A) metaphase.

B) prophase.

C) interphase.

D) prometaphase.

E) anaphase.

B

Nucleoli are present during

A) interphase.

B) prophase.

C) prometaphase.

D) metaphase.

E) anaphase.

A

A particular cyclin called cyclin E forms a complex with a cyclin-dependent kinase called Cdk 2. This complex is important for the progression of the cell from G1 into the S phase of the cell cycle. Which of the following statements is correct?

A) The amount of cyclin E is greatest during the S phase.

B) The amount of Cdk 2 is greater during G1 compared to the S phase.

C) The amount of cyclin E is highest during G1.

D) The amount of Cdk 2 is greatest during G1.

E) The activity of the cyclin E/Cdk 2 complex is highest during G2.

C

Which of the following is (are) true concerning cyclin-dependent kinase (Cdk)?

A) Cdk is inactive, or "turned off," in the presence of cyclin.

B) Cdk is present throughout the cell cycle.

C) Cdk is an enzyme that attaches phosphate groups to other proteins.

D) Both A and B are true.

E) Both B and C are true.

E

Which of the following is true concerning cancer cells?

A) They do not exhibit density-dependent inhibition when growing in culture.

B) When they stop dividing, they do so at random points in the cell cycle.

C) They are not subject to cell cycle controls.

D) B and C only

E) A, B, and C

E

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 amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth.

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 cycle.

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

B

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

The MPF protein complex turns itself off by

A) activating a process that destroys cyclin.

B) activating an enzyme that stimulates cyclin.

C) binding to chromatin.

D) exiting the cell.

E) activating the anaphase-promoting complex.

A

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

An enzyme that attaches a phosphate group to another molecule is called a

A) phosphatase.

B) phosphorylase.

C) kinase.

D) cyclase.

E) ATPase.

C

What is the name of enzymes that control the activities of other proteins by phosphorylating them?

A) ATPases

B) kinases

C) cyclins

D) chromatin

E) protein kinases

B

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

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

A) 12

B) 16

C) 23

D) 46

E) 92

D

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

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

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

A) G0

B) G2

C) G1

D) S

E) M

A

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

A) 10

B) 20

C) 30

D) 40

E) 80

B

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 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

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 DNA.

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

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

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

D

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

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

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

Which of the following organisms does not reproduce cells by mitosis and cytokinesis?

A) cow

B) bacterium

C) mushroom

D) cockroach

E) banana tree

B

Chromosomes first become visible during ________ of mitosis.

A) prometaphase

B) telophase

C) prophase

D) metaphase

E) anaphase

C

Cytoskeletal elements play important roles in cell division. The mitotic spindle apparatus is made of ________ and pulls sister chromatids apart, whereas the contractile ring is made of ________ and required for the separation of daughter cells at the end of the mitotic phase of the cell cycle.

A) intermediate filaments; actin microfilaments

B) microtubules; actin microfilaments

C) microtubules; contractile filaments

D) intermediate filaments; contractile filaments

E) actin microfilaments; myosin

B

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

What causes a 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 MPF complexes

E) the binding of PDGF to receptors on the cell surface

D

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 G2.

A) 8; 8

B) 8; 16

C) 16; 8

D) 16; 16

E) 12; 16

D

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

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

All of the following occur during mitosis except the

A) condensing of chromosomes.

B) uncoupling of chromatids at the centromere.

C) formation of a spindle.

D) synthesis of DNA.

E) disappearance of the nucleolus.

D

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

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

The questions below refer to the following terms. Each term may be used once, more than once, or not at all.

A. telophase

B. anaphase

C. prometaphase

D. metaphase

E. prophase

This is the longest of the mitotic stages.

D

The questions below refer to the following terms. Each term may be used once, more than once, or not at all.

A. telophase

B. anaphase

C. prometaphase

D. metaphase

E. prophase

Centromeres uncouple, sister chromatids are separated, and the two new chromosomes move to opposite poles of the cell.

B

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) cell membrane synthesis

B) spindle fiber formation

C) nuclear envelope breakdown

D) formation of telophase nuclei

E) synthesis of chromatids

D

All of the following occur during prophase of mitosis in animal cells except

A) the centrioles move toward opposite poles.

B) the nucleolus can no longer be seen.

C) the nuclear envelope disappears.

D) chromosomes are duplicated.

E) the spindle is organized.

D

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

In the figure above, mitosis is represented by which number?

A) I

B) II

C) III

D) IV

E) V

D

MPF reaches its threshold concentration at the end of this stage.

A) I

B) II

C) III

D) IV

E) V

C

G1 is represented by which number(s)?

A) I and V

B) II and IV

C) III

D) IV

E) V

A

Which number represents DNA synthesis?

A) I

B) II

C) III

D) IV

E) V

B

Which number represents the point in the cell cycle during which the chromosomes are replicated?

A) I

B) II

C) III

D) IV

E) V

B

The correct sequence of steps in the M phase of the cell cycle is

A) prophase, prometaphase, metaphase, anaphase, telophase.

B) prophase, metaphase, prometaphase, anaphase, telophase.

C) prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis.

D) prophase, metaphase, anaphase, telophase, cytokinesis.

E) cytokinesis, telophase, prophase, prometaphase, metaphase, anaphase.

C

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

Which of the following is false regarding the bacterial chromosome?

A) It consists of a single, circular DNA molecule.

B) DNA replication begins at the origin of replication.

C) Its centromeres uncouple during metaphase of mitosis.

D) It is highly folded within the cell.

E) It has genes that control binary fission.

C

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

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

The data were obtained from a study of the length of time spent in each phase of the cell cycle by cells of three eukaryotic organisms designated beta, delta, and gamma.

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

The data were obtained from a study of the length of time spent in each phase of the cell cycle by cells of three

eukaryotic organisms designated beta, delta, and gamma.

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

The data were obtained from a study of the length of time spent in each phase of the cell cycle by cells of three eukaryotic organisms designated beta, delta, and gamma.

How is the S phase of the cell cycle measured?

A) counting the number of cells produced per hour

B) determining the length of time during which DNA synthesis occurred in the cells

C) comparing the synthesis versus the breakdown of S protein

D) determining when the S chromosome is synthesized

E) stopping G1 and measuring the number of picograms of DNA per cell

B

The following questions consist of five phrases or sentences related to the control of cell division. For each one, select the term below that is most closely related to it. Each term may be used once, more than once, or not at all.

A. PDGF

B. MPF

C. protein kinase

D. cyclin

E. Cdk

released by platelets in the vicinity of an injury

A

The following questions consist of five phrases or sentences related to the control of cell division. For each one, select the term below that is most closely related to it. Each term may be used once, more than once, or not at all.

A. PDGF

B. MPF

C. protein kinase

D. cyclin

E. Cdk

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

C

The following questions consist of five phrases or sentences related to the control of cell division. For each one, select the term below that is most closely related to it. Each term may be used once, more than once, or not at all.

A. PDGF

B. MPF

C. protein kinase

D. cyclin

E. Cdk

Fibroblasts have receptors for this substance on their plasma membranes.

A

The following questions consist of five phrases or sentences related to the control of cell division. For each one, select the term below that is most closely related to it. Each term may be used once, more than once, or not at all.

A. PDGF

B. MPF

C. protein kinase

D. cyclin

E. Cdk

a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically

D

The following questions consist of five phrases or sentences related to the control of cell division. For each one, select the term below that is most closely related to it. Each term may be used once, more than once, or not at all.

A. PDGF

B. MPF

C. protein kinase

D. cyclin

E. Cdk

a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically

E

The following questions consist of five phrases or sentences related to the control of cell division. For each one, select the term below that is most closely related to it. Each term may be used once, more than once, or not at all.

A. PDGF

B. MPF

C. protein kinase

D. cyclin

E. Cdk

triggers the cell's passage past the G2 checkpoint into mitosis

B

The questions below consist of five phrases or sentences concerned with the cell cycle. For each one, select the answer below that is most closely related to it. Each answer may be used once, more than once, or not at all.

1. G0
2. G1
3. S
4. G2
5. M

The "restriction point" occurs here.

B

The questions below consist of five phrases or sentences concerned with the cell cycle. For each one, select the answer below that is most closely related to it. Each answer may be used once, more than once, or not at all.

1. G0
2. G1
3. S
4. G2
5. M

Nerve and muscle cells are in this phase

A

The questions below consist of five phrases or sentences concerned with the cell cycle. For each one, select the answer below that is most closely related to it. Each answer may be used once, more than once, or not at all.

1. G0
2. G1
3. S
4. G2
5. M

the shortest part of the cell cycle

E

The questions below consist of five phrases or sentences concerned with the cell cycle. For each one, select the answer below that is most closely related to it. Each answer may be used once, more than once, or not at all.

1. G0
2. G1
3. S
4. G2
5. M

DNA is replicated at this time of the cell cycle.

C

The questions below consist of five phrases or sentences concerned with the cell cycle. For each one, select the answer below that is most closely related to it. Each answer may be used once, more than once, or not at all.

1. G0
2. G1
3. S
4. G2
5. M

The cyclin component of MPF is destroyed toward the end of this phase.

E

What is a genome?

A) the complete complement of an organism's genes

B) a specific sequence 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

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) Under normal circumstances, each chromosome contains precisely one gene.

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

D

Asexual reproduction and sexual reproduction are different in that

A) individuals reproducing asexually transmit 100% of their genes to their progeny, whereas individuals reproducing sexually only transmit 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 only requires mitosis, whereas sexual reproduction always involves meiosis.

E) all of the above

E

How do the two members of a pair of homologous chromosomes differ from each other?

A) their length

B) the identity and relative position of the genes present on each of the chromosomes

C) their staining patterns

D) the position of the centromere within each of the chromosomes

E) the precise sequence of the DNA within each of the chromosomes

E

What is a karyotype?

A) the set of unique physical characteristics that define an individual

B) the collection of all the mutations present within a genome

C) a unique combination of chromosomes found in a gamete

D) a system of classifying cell nuclei

E) a display of every pair of homologous chromosomes within a cell, organized according to size and shape

E

By examining a karyotype, it is possible to determine

A) which of two related plant forms is a gametophyte, and which is a sporophyte.

B) the sex of an animal.

C) the age of a fungus.

D) A and B only

E) A, B, and C

D

At which stage of mitosis are chromosomes photographed in the preparation of a karyotype?

A) prophase

B) metaphase

C) anaphase

D) telophase

E) interphase

B

The human X and Y chromosomes are

A) both present in every somatic cell of males and females alike.

B) of approximately equal size.

C) almost entirely homologous, despite their different names.

D) called "sex chromosomes" because they determine an individual's sex.

E) all of the above

D

If the liver cells of an animal have 24 chromosomes, how many chromosomes do its sperm cells have?

A) 6

B) 12

C) 24

D) 48

E) 64

B

Which of the following is true of a species that has a chromosome number of 2n = 16?

A) The species is diploid with 32 chromosomes.

B) The species has 16 sets of chromosomes.

C) There are 8 homologous pairs.

D) During the S phase of the cell cycle, there will be 32 separate chromosomes.

E) A gamete from this species has 4 chromosomes.

C

Which of the following is the term for a human cell that contains 22 pairs of autosomes and two X chromosomes?

A) an unfertilized egg cell

B) a sperm cell

C) a male somatic cell

D) a female somatic cell

E) both A and D

D

Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do all sexual life cycles have in common?

I. alternation of generations

II. meiosis

III. fertilization

IV. gametes

V. spores

A) I, IV, and V

B) I, II, and IV

C) II, III, and IV

D) II, IV, and V

E) all of the above

C

Which of these statements is false?

A) In humans, each of the 22 maternal autosomes has a homologous paternal chromosome.

B) In humans, the 23rd pair, the sex chromosomes, determine whether the person is female (XX) or male (XY).

C) Single, haploid (n) sets of chromosomes in ovum and sperm unite during fertilization, forming a diploid (2n), single-celled zygote.

D) At sexual maturity, ovaries and testes produce diploid gametes by meiosis.

E) Sexual life cycles differ with respect to the relative timing of meiosis and fertilization.

D

In animals, meiosis results in gametes, and fertilization results in

A) spores.

B) gametophytes.

C) zygotes.

D) sporophytes.

E) clones

C

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

A) sporophyte meiosis

B) gametophyte mitosis

C) gametophyte meiosis

D) sporophyte mitosis

E) alternation of generations

B

Which of the following is an example of alternation of generations?

A) A grandparent and grandchild each have dark hair, but the parent has blond hair.

B) A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).

C) A diploid animal produces gametes by meiosis, and the gametes undergo fertilization to produce a diploid zygote.

D) A haploid mushroom produces gametes by mitosis, and the gametes undergo fertilization, which is immediately followed by meiosis.

E) A diploid cell divides by mitosis to produce two diploid daughter cells, which then fuse to produce a tetraploid cell.

B