Biology Chapter 8 Mastering Biology

How many pairs of autosomes do humans have? 22 2 23 1

22

Imagine that a human skin cell went through mitosis but did not undergo cytokinesis. How many chromosomes would be in the cell? A. 92 B. 23 C. 69 D. 46

A. 92

Which events occur during prophase? Check all that apply. A. Chromosomes condense and are attached to spindle fibers. B. The nuclear envelope breaks down. C. Chromosomes are replicated. D. The sister chromatids break apart and begin to separate.

A. Chromosomes condense and are attached to spindle fibers. B. The nuclear envelope breaks down.

The first step of bacterial replication is _____. A. DNA replication B. attachment of the DNA to the plasma membrane C. pinching of the plasma membrane D. separation of daughter cells

A. DNA replication

Inbreeding has a number of interesting effects. For one, highly in-bred strains (varieties) may carry identical forms of every gene. Mice have 40 chromosomes in their diploid (2n) set. How many genetically distinct kinds of gametes (gametes with different genetic characteristics) could be produced through meiosis in an in-bred strain where there are identical forms of every gene? 20 1 million 1 1 trillion

1

An example of a cell that is 2n is a _____. A. sperm or ovum B. somatic cell C. haploid cell D. gametophyte

B. somatic cell

An example of a cell that is 2n is a __________. A. haploid cell B. somatic cell C. sperm or ovum D. gametophyte

B. somatic cell

An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis? eight two four one

four

In a cell with eight chromosomes, one chiasma develops during meiosis I in only one particular pair of homologs. How many recombinant chromosomes will there be at the completion of meiosis II? four one eight two

two

The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis? A. Prophase B. Anaphase C. Telophase D. Interphase E. Metaphase

A. Prophase

The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis? A. Telophase B. Interphase C. Anaphase D. Prophase E. Metaphase

A. Telophase

You and your lab partner are observing a cell under a microscope, but you do not know whether it is a eukaryote or a prokaryote. Which of the following observations regarding the chromosomes would you use to immediately conclude that the A. The chromosomes are housed in a membrane-enclosed nucleus. B. The chromosomes are very simple in structure. C. The chromosomes contain very few proteins. D. The chromosomes are circular in structure.

A. The chromosomes are housed in a membrane-enclosed nucleus.

The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis? A. Prophase B. Metaphase C. Anaphase D. Interphase E. Telophase

C. Anaphase

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. There are _____ chromatids. 23 23 or 46, depending on when during prophase you look 92 46

92

The _____ separate in meiosis I; the _____ separate in meiosis II. A. homologous chromosomes ... sister chromatids B. sister chromatids ... homologous chromosomes C. centrosomes ... centromeres D. sister chromatids ... tetrads

A. homologous chromosomes ... sister chromatids

Two chromosomes in a nucleus that carry genes controlling the same inherited characteristics are A. homologous chromosomes. B. parallel chromosomes. C. heterologous chromosomes. D. complementary chromosomes.

A. homologous chromosomes.

In anaphase I, _____. A. the sister chromatids move randomly toward either pole B. homologous chromosomes move toward opposite poles C. homologous chromosomes move randomly toward either pole D. the sister chromatids move toward opposite poles

B. homologous chromosomes move toward opposite poles

In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____. A. metaphase B. prophase C. interphase D. anaphase

B. prophase

Synapsis occurs during _____. A. telophase I B. prophase I C. prophase II D. anaphase I

B. prophase I

During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur? A. anaphase I. B. prophase I. C. meiosis II. D. telophase I. E. Metaphase I.

B. prophase I.

At a critical point in meiosis, the chromosomes do not replicate. This occurs between _____. A. anaphase I and telophase I B. telophase I and prophase II C. prophase I and metaphase I D. metaphase I and anaphase I

B. telophase I and prophase II

During _____ both the contents of the nucleus and the cytoplasm are divided. A. S B. the mitotic phase C. G2 D. G1 E. mitosis

B. the mitotic phase

A cell is initially diploid, but it has a unique cell cycle in that this cell goes through two S phases instead of one. What would the remainder of its cell cycle consist of if this cell is to produce four identical diploid daughter cells at the end of its cell cycle? A. two rounds of mitosis and two rounds of cytokinesis B. one round of mitosis and two rounds of cytokinesis C. two rounds of mitosis and one round of cytokinesis D. one round of mitosis and one round of cytokinesis

A. two rounds of mitosis and two rounds of cytokinesis

Gametes are produced by _____. A. fertilization B. the cell cycle C. meiosis D. mitosis E. asexual reproduction

C. meiosis

Normal human gametes carry _____ chromosomes. A. 46 B. 23 pairs of C. 5 D. 46 pairs of E. 23

E. 23

Centromeres divide and sister chromatids become full-fledged chromosomes during _____. A. telophase B. prometaphase C. interphase D. metaphase E. anaphase

E. anaphase

Meiosis starts with a single diploid cell and produces A. two diploid cells. B. two haploid cells. C. four diploid cells. D. eight haploid cells. E. four haploid cells.

E. four haploid cells.

During _____ the cell grows and replicates both its organelles and its chromosomes. A. G1 B. S C. cytokinesis D. mitosis E. interphase

E. interphase

C. E

Which of these phases encompasses all of the stages of mitosis? A. D B. C C. E D. B E. A

Which of the following indicates Turner syndrome? A. XXY B. XXX C. XYY D. XO

D. XO

Mitosis and cytokinesis result in the formation of _____; meiosis and cytokinesis result in the formation of _____. A. two diploid cells ... two diploid cells B. two diploid cells ... four haploid cells C. two diploid cells ... two haploid cells D. four diploid cells ... four haploid cells

B. two diploid cells ... four haploid cells

During which phase of mitosis does the nuclear envelope re-form? A. prophase B. anaphase C. telophase D. metaphase

C. telophase

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes. A. 32 B. 8 C. 30 D. 16 E. 64

D. 16

What is the difference between a benign tumor and a malignant tumor? A. Benign tumors will not kill you; malignant tumors will. B. Benign tumors metastasize; malignant tumors do not. C. Benign tumors are a mass of essentially abnormal cells; malignant tumors are an abnormal mass of essentially normal cells. D. Benign tumors do not metastasize; malignant tumors do.

D. Benign tumors do not metastasize; malignant tumors do.

Which of the following occurs during mitosis? A. Organelles replicate. B. Two genetically different daughter cells result. C. Chromosomes replicate. D. Chromatids separate.

D. Chromatids separate.

Immune system cells enter a resting phase after undergoing mitosis. When activated - for example, by an infection - they can reenter the sequence of events in the cell cycle that leads to cell division. What would be the correct sequence of events? View Available Hint(s) A. S, G1, G2, M B. G1, G2, S, M C. G1, M, G2, S, G1 D. G1, S, G2, M

D. G1, S, G2, M

The chromosomes line up in the center of the cell during which phase of mitosis? A. Anaphase B. Telophase C. Interphase D. Metaphase E. Prophase

D. Metaphase

Looking through a light microscope at a dividing cell, you see two separate groups of chromosomes on opposite ends of the cell. New nuclear envelopes are taking shape around each group. The chromosomes then begin to disappear as they unwind. You are witnessing _____. A. metaphase B. prophase C. anaphase D. telophase

D. telophase

During mitosis, the chromosomes move because _____. A. of the duplication of the centrosome B. they slide along microfilament bundles C. they diffuse within the nucleus to areas where they are less concentrated D. they attach to a dynamic, precisely regulated mitotic spindle

D. they attach to a dynamic, precisely regulated mitotic spindle

True or false. Mitosis takes place during M phase of the cell cycle, which is longer than interphase. True False

False

The function(s) of meiosis is/are _____. a. reproduction (production of gametes) b. growth and development c. tissue repair/replacement of damaged cells b and c, but not a a, b, and c

a. reproduction (production of gametes)

How many pairs of autosomes do humans have? 23 1 2 22

22

A human somatic cell contains _____ chromosomes. 2n 47 46 23

46

Bacteria divide by: A. binary fission B. meiosis C. sexual reproduction D. mitosis

A. binary fission

A cleavage furrow forms in an animal cell during _____. A. anaphase B. cytokinesis C. G1 phase D. metaphase

B. cytokinesis

Single sister chromatids are found in cells at mitotic _____. A. prophase and telophase B. prophase and anaphase C. anaphase and telophase D. metaphase and anaphase

C. anaphase and telophase

When animal cells are grown in a petri dish, they typically stop dividing once they have formed a single, unbroken layer on the bottom of the dish. This arrest of division is an example of A. cell constraint. B. cell division repression. C. growth factor desensitization. D. density-dependent inhibition.

D. density-dependent inhibition.

In bacterial cells, binary fission involves __________. A. formation of a cell plate B. prophase, metaphase, anaphase, and telophase C. disintegration of the nuclear membrane D. distribution of a copy of the single parental chromosome to each daughter cell

D. distribution of a copy of the single parental chromosome to each daughter cell

Fertilization joins _____ to produce a _____. A. diploid zygotes ... gamete B. haploid zygotes ... diploid gamete C. homologous chromosomes ... tetrad D. haploid gametes ... diploid zygote

D. haploid gametes ... diploid zygote

Nucleoli are present during _____. A. anaphase B. prophase C. prometaphase D. interphase E. metaphase

D. interphase

There are species of coffee plant with 22, 44, 66, and 88 chromosomes. All but one of these species is considered to be an example of polyploidy. Plant geneticists believe that the original haploid number of chromosomes in coffee was _____. 23 22 11 44

11

Baker's yeast is an organism with 32 chromosomes that can perform asexual or sexual reproduction and exist as both a diploid and haploid cell. After meiosis, how many chromosomes will be present in each cell? 8 64 32 16

16

A certain species of animal has six pairs of chromosomes. How many DNA molecules are present in the nuclei of these animals during G2 phase? 6 48 24 12

24

If we assume that crossing over does not occur, how many different combinations of chromosomes are possible in a zygote derived from diploid parents who each have three pairs of chromosomes? 6 8 million 8 64

64

Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16? A. Extra copies of the other somatic chromosomes are probably fatal. B. Nondisjunction of chromosomes 3 and 16 probably occurs more frequently. C. There are probably more genes on chromosome 21 than on either chromosomes 3 or 16. D. Down syndrome results in more serious symptoms than either trisomy 3 or trisomy 16.

A. Extra copies of the other somatic chromosomes are probably fatal.

Crossing over is important because it _____. A. allows the exchange of genes between homologous chromosomes B. holds tetrads together C. prevents variation in gametes D. ensures that homologous chromosomes pair up

A. allows the exchange of genes between homologous chromosomes

Which of the following conditions would result in inhibition of cell division due to density-dependent factors? A. being completely surrounded by other cells B. being attached to other cells of the same tissue C. presence of growth factors D. being attached to an extracellular surface

A. being completely surrounded by other cells

Asexual and sexual reproduction differ in that sexual reproduction _____. A. can produce great variation among the offspring B. will produce offspring identical to the parents C. is the only way multicellular organisms can reproduce D. is the only way single-celled organisms can reproduce

A. can produce great variation among the offspring

Meiosis starts with _____ cells and produces _____ gametes. A. diploid ... haploid B. diploid ... diploid C. haploid ... haploid D. haploid ... diploid

A. diploid ... haploid

During anaphase I, _____. A. homologues separate and migrate toward opposite poles B. chromosomes line up in one plane C. sister chromatids separate and migrate toward opposite poles D. nuclear membranes re-form

A. homologues separate and migrate toward opposite poles

During _____, the cell carries out its normal functions and the chromosomes are thinly spread out throughout the nucleus. A. interphase B. prophase C. metaphase D. anaphase E. telophase

A. interphase

A fragment of chromosome 21 reattaches to chromosome 21, but in the reverse direction. What is the name given to this change? A. inversion B. duplication C. trisomy 21 D. deletion

A. inversion

If it weren't for _____, chromosome number would double with every generation of sexual reproduction. A. meiosis B. mitosis C. crossing over D. fertilization

A. meiosis

During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____. A. nondisjunction B. gametic infertility C. sticky chiasmata D. meiotic failure

A. nondisjunction

In meiosis II, _____. A. sister chromatids are separated B. chromosome number is reduced from diploid to haploid C. homologous chromosomes pair to ensure their even distribution to daughter cells D. chromosomes cross over to exchange genetic information

A. sister chromatids are separated

Mitosis occurs in _____; meiosis occurs in _____. A. somatic or body cells ... germ cells in the testes or ovaries B. germ cells in the testes or ovaries ... somatic or body cells C. sexually reproducing organisms ... asexually reproducing organisms D. adult organisms ... zygotes and early embryos

A. somatic or body cells ... germ cells in the testes or ovaries

Mitosis and cytokinesis result in the formation of __________; meiosis and cytokinesis result in the formation of __________. A. two diploid cells : four haploid cells B. two diploid cells : two diploid cells C. two diploid cells : two haploid cells D. four diploid cells : four haploid cells

A. two diploid cells : four haploid cells

In the laboratory, cancer cells fail to show density-dependent inhibition of growth in cell culture. What is one explanation that could account for this? A. Cancer cells have inactive receptors for growth factors. B. Cancer cells continuously secrete growth factors into the cell culture medium. C. Cancer cells are unable to attach to a surface and grow. D. Cancer cells continue to die at a rate that is equal to their growth.

B. Cancer cells continuously secrete growth factors into the cell culture medium.

Which of the following statements regarding cell division is false? A. Cell division can reproduce an entire organism. B. Cell division is common in eukaryotes but rare in prokaryotes. C. Cell division is the basis of both sexual and asexual reproduction. D. Cell division is necessary for development to occur.

B. Cell division is common in eukaryotes but rare in prokaryotes.

Which of the following statements correctly describes the timing of DNA synthesis? A. DNA is synthesized continuously. B. DNA is synthesized in the S phase of interphase. C. DNA is synthesized only during mitosis. D. DNA is synthesized in G2 of interphase immediately preceding mitosis.

B. DNA is synthesized in the S phase of interphase.

Which of the following statements regarding genetic diversity is false? A. Genetic diversity is enhanced by crossing over during meiosis. B. Genetic diversity is enhanced by mitosis. C. Genetic diversity is enhanced by random fertilization. D. Genetic diversity is enhanced by independent orientation of chromosomes at metaphase I.

B. Genetic diversity is enhanced by mitosis.

During binary fission, the replicated bacterial chromosome attaches to the plasma membrane by specialized anchor proteins. What is the purpose of this attachment between chromosome and membrane? A. It causes the cell to elongate. B. It ensures the separation of the replicated chromosomes as new membrane is made. C. It ensures the formation of two complete nuclei around each of the chromosomes. D. This keeps the separate chromosomes together.

B. It ensures the separation of the replicated chromosomes as new membrane is made.

Which of the following statements regarding mitosis and meiosis is false? A. Mitosis provides for growth and tissue repair. B. Meiosis provides for asexual reproduction. C. In mitosis, the chromosomes replicate only once in the preceding interphase. D. All the events unique to meiosis occur during meiosis I.

B. Meiosis provides for asexual reproduction.

During meiosis I, homologous chromosomes form a tetrad. What does this accomplish? A. Crossing over can occur, creating new combinations of chromosomes through their independent alignment across the metaphase plate. B. This brings the chromosomes into alignment so that crossing over can create new combinations of genes present on a single chromosome. C. A chiasma forms as crossing over occurs, which ultimately reduces the number of chromatids per chromosome. D. It allows for the process of crossing over to occur, which reduces the number of chromosomes present in the cell.

B. This brings the chromosomes into alignment so that crossing over can create new combinations of genes present on a single chromosome.

In many organisms, including humans, chromosomes are found in homologous pairs. Homologous chromosomes _____. A. have roughly similar arrangements of their genes, but some versions of the genes may differ between the chromosomes B. are identical in the arrangement of their genes, but some versions of the genes may differ between the chromosomes C. are similar in size and shape, but this deceptive similarity has nothing to do with placement of gene arrangement or type D. are identical both in the arrangement of their genes and in every version of every gene

B. are identical in the arrangement of their genes, but some versions of the genes may differ between the chromosomes

Strictly speaking, the phrase "like begets like" refers to A. production of gametes from a premeiotic cell. B. asexual reproduction only. C. sexual reproduction only. D. all forms of reproduction.

B. asexual reproduction only.

A cell replicates its entire chromosomal DNA only __________. A. when the cell needs RNA B. before it is about to divide C. to repair damage caused by mutation D. when it makes protein

B. before it is about to divide

Asexual and sexual reproduction differ in that sexual reproduction _____. A. is the only way multicellular organisms can reproduce B. can produce great variation among the offspring C. will produce offspring identical to the parents D. is the only way single-celled organisms can reproduce

B. can produce great variation among the offspring

At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________. A. replication B. cytokinesis C. meiosis D. condensation E. telophase

B. cytokinesis

A cell is treated with a drug that prevents the formation of vesicles. Which of the following processes depends on the formation of vesicles and would therefore be blocked? A. cytokinesis in an animal cell B. cytokinesis in a plant cell C. separation of eukaryotic chromosomes at anaphase D. alignment of eukaryotic chromosomes at the metaphase plate

B. cytokinesis in a plant cell

Cytokinesis refers to _____. A. division of all the parts of the cell B. division of the cell outside the nuclear material C. division of the nucleus D. cell movement

B. division of the cell outside the nuclear material

The diploid phase of the human life cycle begins with _____. A. mitosis B. fertilization C. meiosis D. the first division of the zygote

B. fertilization

In sexually reproducing multicellular organisms, the main functions of mitosis are _____. Check all that apply. A. reproduction (production of gametes) B. growth and development C. tissue repair/replacement of damaged cells

B. growth and development C. tissue repair/replacement of damaged cells

At a chiasma, two ________ are attached to each other. A. homologous or sister chromatids B. homologous or nonsister chromatids C. nonhomologous chromosomes D. daughter cells

B. homologous or nonsister chromatids

A cell preparing to undergo meiosis duplicates its chromosomes during A. prophase I. B. interphase. C. anaphase I. D. meiosis II. E. metaphase I.

B. interphase.

When we say that an organism is haploid, we mean that _____. A. its cells each have one chromosome B. its cells each have one set of chromosomes C. Its cells have one half of a chromosome D. its cells each have two sets of chromosomes

B. its cells each have one set of chromosomes

Looking through a light microscope at a cell undergoing meiosis, you see that the chromosomes have joined into XX-shaped tetrads. These tetrads are lined up along a plane that runs through the center of the cell. This cell is in _____. A. interphase B. meiosis I C. meiosis II D. cytokinesis of meiosis II

B. meiosis I

Looking through a light microscope at a cell undergoing division, you see that the condensed chromosomes have lined up along the midline of the cell. The homologous pairs are NOT joined in tetrads. Each chromosome takes its own place in line, independentof its homolog. You are witnessing _____. A. interphase B. metaphase of mitosis C. metaphase of meiosis I D. telophase of either mitosis or meiosis II

B. metaphase of mitosis

Consider the process by which bacterial populations grow. What process performs a similar function in humans? A. transformation B. mitosis C. binary fission D. meiosis

B. mitosis

If these four cells resulted from cell division of a single cell with diploid chromosome number 2n = 4, what best describes what just occurred? A. inversion B. nondisjunction C. translocation D. normal meiosis

B. nondisjunction

At which point do centrosomes begin to move apart to the opposite poles of the cell in a dividing human liver cell? A. metaphase B. prophase C. G2 phase D. S phase

B. prophase

Meiosis is typically accomplished in _____. A. one step. A diploid cell divides to produce two haploid gametes. B. three steps. All of the chromosomes are duplicated in a diploid cell, and then there are two cell divisions to produce a total of four haploid gametes. C. two steps. A diploid cell divides to produce two haploid gametes; these are then duplicated to produce a total of four gamete cells.

B. three steps. All of the chromosomes are duplicated in a diploid cell, and then there are two cell divisions to produce a total of four haploid gametes.

Which of the following checkpoints does not occur late in G1? A. A check that the cell is large enough for division B. A check that nutrients are sufficient C. A check that chromosome replication has been successfully completed D. A check that growth factors are present

C. A check that chromosome replication has been successfully completed

Polyploidy is involved in which of the following examples? A. Some plants alternate between haploid and diploid phases. B. XYY males C. A normal watermelon has 22 chromosomes but seedless watermelons have 33 chromosomes. D. XO females

C. A normal watermelon has 22 chromosomes but seedless watermelons have 33 chromosomes.

Which of the following statements is false? A. A zygote is a fertilized egg. B. Two haploid cells fuse during fertilization. C. An X chromosome is an autosome. D. Gametes are haploid cells.

C. An X chromosome is an autosome.

In the laboratory, cancer cells fail to show density-dependent inhibition of growth in cell culture. What is one explanation that could account for this? A. Cancer cells continue to die at a rate that is equal to their growth. B. Cancer cells have inactive receptors for growth factors. C. Cancer cells continuously secrete growth factors into the cell culture medium. D. Cancer cells are unable to attach to a surface and grow.

C. Cancer cells continuously secrete growth factors into the cell culture medium.

Scientists commonly choose white blood cells that are going through mitosis to prepare karyotypes. Why? A. More cells are in mitosis than any other stage of the cell cycle, making it easier to obtain mitotic cells for study. B. Cells in mitosis contain the greatest number of chromosomes, thus providing more material for study. C. During mitosis, chromosomes are more condensed than during interphase. D. Cells in mitosis have the fewest chromosomes, thus simplifying karyotype analysis.

C. During mitosis, chromosomes are more condensed than during interphase.

When examining cells in the laboratory, you notice that a particular cell has half as much DNA as the surrounding cells. It appears that this cell's cell cycle halted at checkpoint _____. A. M phase B. G0 C. G1 D. G2

C. G1

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication? A. In both cases there would be an extra chromosome, but in trisomy there would be three chromatids on one chromosome and in a duplication there would be two chromatids on one chromosome. B. The chromosome number in both cases would be normal, but in trisomy there would be three chromatids on one chromosome and in a duplication there would be two chromatids on one chromosome. C. In trisomy there would be one extra chromosome; in a duplication, one chromosome would have two copies of a portion of the chromosome. D. The chromosome number in trisomy would be normal; in a duplication, there would be one more chromosome.

C. In trisomy there would be one extra chromosome; in a duplication, one chromosome would have two copies of a portion of the chromosome.

Which of the following statements regarding mitosis and meiosis is true? A. In metaphase of mitosis and metaphase I of meiosis, homologous chromosomes separate. B. Mitosis takes place in your gametes, whereas meiosis takes place in your somatic cells. C. Sister chromatids separate during anaphase of mitosis and anaphase II of meiosis. D. Independent orientation occurs during metaphase of mitosis and metaphase II of meiosis.

C. Sister chromatids separate during anaphase of mitosis and anaphase II of meiosis.

Which event occurs only during prophase I of the first meiotic division? A. Chromosomes contain two chromatids attached to the same centromere. B. Replication of DNA takes place. C. Synapsis of homologous pairs occurs. D. Nuclear membrane breaks down.

C. Synapsis of homologous pairs occurs.

What must happen before a cell can begin mitosis? View Available Hint(s) A. The nuclear envelope must break up. B. The nucleus must divide in two. C. The chromosomes must be duplicated. D. A mitotic spindle must form. E. The sister chromatids must be separated.

C. The chromosomes must be duplicated.

During cell division, what role do centrosomes play? A. They are required for DNA replication. B. They are the structures that hold the two sister chromatids together. C. They organize the microtubules. D. They cause cytokinesis via the concentric shortening of microtubules.

C. They organize the microtubules.

Which of the following occurs during mitosis? A. Two genetically different daughter cells result. B. Chromosomes replicate. C. Two daughter nuclei, one at each pole of the cell, are generated. D. Organelles replicate.

C. Two daughter nuclei, one at each pole of the cell, are generated.

In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos? A. Two of the embryos will be trisomic for chromosome 18, and two will be normal. B. Two of the embryos will be normal, and two will contain a single copy of chromosome 18. C. Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18. D. All four embryos will be trisomic for chromosome 18.

C. Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.

Mr. and Mrs. Smith have three sons in elementary school. Two of their children are progressing normally, but their youngest son, Charles, has been much slower than his siblings in developing speech and language skills. His parents are concerned that he has a learning disability and decide to investigate further. Since some learning disabilities can be genetically based, their pediatrician recommends a chromosomal analysis. The results show that Charles has a trisomy of the sex chromosomes, diagnosed as XYY, which is caused by nondisjunction in the formation of the father's sperm. The nondisjunction resulted in an extra copy of the Y chromosome. The extra copy was passed on to Charles during fertilization. Most often, this chromosomal change causes no unusual physical features or medical problems, but those with trisomy of the sex chromosomes do have a higher than normal risk of delays in learning development. If Charles gets married and starts a family, which of the following chromosomal abnormalities has an increased chance of occurring in his children? A. YO B. XO C. XXY D. YY

C. XXY

A cell is treated with a drug that prevents the formation of intracellular (within the cell) vesicles. Which of the following processes would be blocked? A. separation of eukaryotic chromosomes at anaphase B. alignment of eukaryotic chromosomes at the metaphase plate C. cytokinesis in a plant cell D. cytokinesis in an animal cell

C. cytokinesis in a plant cell

A cell is treated with a drug that prevents the formation of vesicles. Which of the following processes depends on the formation of vesicles and would therefore be blocked? A. separation of eukaryotic chromosomes at anaphase B. cytokinesis in an animal cell C. cytokinesis in a plant cell D. alignment of eukaryotic chromosomes at the metaphase plate

C. cytokinesis in a plant cell

When forming buds, hydras _____. A. allow their homologous chromosomes to cross over B. divide by meiosis C. divide by mitosis D. differentiate into somatic cells

C. divide by mitosis

Cytokinesis _____. A. produces two new nuclear envelopes B. duplicates the chromosomes, setting the stage for cell division C. finishes mitosis by dividing the cytoplasm and organelles of the original parent cell into two separate daughter cells D. lines up the paired chromatids along the center of the cell in preparation for anaphase

C. finishes mitosis by dividing the cytoplasm and organelles of the original parent cell into two separate daughter cells

Chromatids are _____. A. not present in the Y sex chromosome, but present in the X sex chromosome B. found only in aberrant chromosomes C. identical copies of each other if they are part of the same chromosome D. held together by the centrioles

C. identical copies of each other if they are part of the same chromosome

When we say that an organism is haploid, we mean that _____. A. it has one half of a chromosome B. its cells each have one chromosome C. its cells each have one set of chromosomes D. its cells each have two sets of chromosomes

C. its cells each have one set of chromosomes

After fertilization, the resulting zygote begins to divide by _____. A. binary fission B. schizogony C. mitosis D. meiosis

C. mitosis

Duplication of the chromosomes to produce sister chromatids _____. A. occurs in meiosis but not in mitosis B. occurs in mitosis but not in meiosis C. occurs in both mitosis and meiosis D. does not occur in either type of cell division

C. occurs in both mitosis and meiosis

Independent orientation of chromosomes at metaphase I results in an increase in the number of A. sex chromosomes. B. gametes. C. possible combinations of characteristics. D. homologous chromosomes.

C. possible combinations of characteristics.

The correct order of events during meiosis is A. prophase I, anaphase I, metaphase I, telophase I, meiosis II, cytokinesis. B. metaphase I, prophase I, anaphase I, telophase I, cytokinesis, meiosis II. C. prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II. D. prophase I, anaphase I, telophase I, metaphase I, meiosis II. E. metaphase I, prophase I, telophase I, anaphase I, cytokinesis, meiosis II.

C. prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.

Which of the following helps maintain the structure of chromosomes and control the activity of genes? A. ribosomes B. the nuclear membrane C. proteins D. centromeres

C. proteins

The exchange of parts between nonhomologous chromosomes is called _____. A. crossing over B. inversion C. reciprocal translocation D. transformation

C. reciprocal translocation

Cytokinesis often, but not always, accompanies _____. A. prometaphase B. metaphase C. telophase D. interphase E. anaphase

C. telophase

DNA replication occurs in _____. A. metaphase of meiosis only B. prophase of both mitosis and meiosis C. the S phase of interphase D. the G1 phase of interphase in reproductive cells only

C. the S phase of interphase

Crossing over is _____. A. the formation of tetrads B. an independent assortment of chromosomes C. the exchange of homologous portions of nonsister chromatids D. the movement of genetic material from one chromosome to a nonhomologous chromosome

C. the exchange of homologous portions of nonsister chromatids

During prophase a homologous pair of chromosomes consists of _____. A. two chromosomes and two chromatids B. one chromosome and two chromatids C. two chromosomes and four chromatids D. one chromosome and four chromatids E. four chromosomes and two chromatids

C. two chromosomes and four chromatids

Immune system cells enter a resting phase after undergoing mitosis. When activated—for example, by an infection—they can reenter the sequence of events in the cell cycle that leads to cell division. What would be the correct cell cycle sequence of events for these reactivated cells? A. S, G1, G2, M B. G1, G2, S, M C. G1, M, G2, S, G1 D. G1, S, G2, M

D. G1, S, G2, M

Trisomy for most autosomes is fatal, yet trisomy or even tetrasomy (four copies) of the X chromosome is not. What is the explanation for this difference? A. The X chromosome does not carry any genes. B. There is a mechanism to keep only two X chromosomes active, regardless of the total number. C. The number of X chromosomes is always balanced by the number of Y chromosomes. D. Only one copy of the X chromosome is active, regardless of the total number of X chromosomes.

D. Only one copy of the X chromosome is active, regardless of the total number of X chromosomes.

Which of the following statements regarding the cell cycle control system is false? A. The cell cycle control system includes three key checkpoints to complete a cell cycle. B. The cell cycle control system triggers and controls major events in the cell cycle. C. The cell cycle control system receives messages from outside the cell that influence cell division. D. The cell cycle control system operates independently of the growth factors.

D. The cell cycle control system operates independently of the growth factors.

What would be the immediate consequence of destroying a cell's centrosomes? A. The nuclear envelope could never re-form. B. Sister chromatids would lose their centromeres. C. The nuclear envelope would never break down. D. The mitotic spindle would not form.

D. The mitotic spindle would not form.

What would be the immediate consequence of destroying a cell's centrosomes? A. The nuclear envelope would never break down. B. The nuclear envelope could never re-form. C. Sister chromatids would lose their centromeres. D. The mitotic spindle would not form.

D. The mitotic spindle would not form.

Within one chromosome, what is the relationship between the sequence of bases in DNA of one sister chromatid compared to the other? A. The sequence in one chromatid is complementary to the sequence in the other. B. The sequences are similar, but not identical. C. The sequences are unrelated. D. The sequences are identical.

D. The sequences are identical.

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not? A. Trisomy for these other autosomal chromosomes occurs so rarely that it has never been documented. B. These autosomal chromosomes do not contain the same type of DNA or protein that makes up chromosomes susceptible to trisomy. C. Trisomy for these autosomal chromosomes has no effect and therefore would never be noticed. D. Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

D. Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called A. sister chromosomes. B. nucleoli. C. chromatin. D. sister chromatids.

D. sister chromatids.

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not? A. These autosomal chromosomes do not contain the same type of DNA or protein that makes up chromosomes susceptible to trisomy. B. Trisomy for these other autosomal chromosomes occurs so rarely that it has never been documented. C. Trisomy for these autosomal chromosomes has no effect and therefore would never be noticed. D. Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

D. Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

What is different concerning the DNA in bacterial cells as opposed to eukaryotic cells? A. the amount of DNA present B. whether the DNA is housed in a nucleus or not C. whether the DNA is linear or circular D. all of the above are differences between prokaryotic and eukaryotic DNA

D. all of the above are differences between prokaryotic and eukaryotic DNA

If a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction, the resulting chromosomal abnormality is called _____. A. a deletion B. a nondisjunction C. a reciprocal translocation D. an inversion

D. an inversion

The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____. A. cytokinesis B. metaphase C. telophase D. anaphase

D. anaphase

The stage of mitosis during which the chromosomes move toward separate poles of the cell is _____. A. cytokinesis B. metaphase C. telophase D. anaphase

D. anaphase

The function of mitosis is to produce daughter cells that _____. A. have half the number of chromosomes B. have a random assortment of maternal and paternal chromosomes C. have the same number of chromosomes as the parent cell but not the same genetic content D. are genetically identical to the parent cell (assuming no mutation has occurred)

D. are genetically identical to the parent cell (assuming no mutation has occurred)

A cell replicates its entire chromosomal DNA only _____. A. when it makes protein B. when the cell needs RNA C. to repair damage caused by mutation D. before it is about to divide

D. before it is about to divide

A benign and a malignant tumor differ in that _____. A. a benign tumor only forms from solid tissues such as skin or muscle and a malignant tumor only forms from blood and lymphatic tissue B. benign tumors are harmless and malignant tumors are lethal C. cells of a benign tumor spread by metastasis and cells of a malignant tumor spread by expansion of the tumor mass D. cells of a benign tumor remain within the tumor, whereas cells of a malignant tumor can spread to other body tissues

D. cells of a benign tumor remain within the tumor, whereas cells of a malignant tumor can spread to other body tissues

During prophase I of meiosis, A. there are two daughter cells, each with 23 chromosomes. B. the homologous chromosomes separate and move towards opposite poles. C. there are four haploid daughter cells. D. homologous chromosomes stick together in pairs. E. chromosome pairs are positioned in the middle of the cell.

D. homologous chromosomes stick together in pairs.

In humans, the _____ determines the sex of the offspring because _____. A. female ... only the female provides cytoplasm to the zygote B. female ... only the female has two functional sex chromosomes C. male ... the sperm can fertilize either a female egg or a male egg D. male ... the male can contribute either an X or a Y chromosome

D. male ... the male can contribute either an X or a Y chromosome

During which phase of mitosis do the chromosomes line up on a plane equidistant from the two spindle poles? A. anaphase B. prophase C. telophase D. metaphase

D. metaphase

Asexual reproduction _____. A. leads to a loss of genetic material B. produces offspring that always look exactly like the parent C. is limited to plants D. produces offspring genetically identical to the parent

D. produces offspring genetically identical to the parent

The term binary fission is best applied to _____. A. mitosis B. nuclear chemistry C. plants D. prokaryotes

D. prokaryotes

Spindle fibers attach to kinetochores during _____. A. telophase B. anaphase C. interphase D. prometaphase E. metaphase

D. prometaphase

Chromosomes become visible during _____. A. interphase B. prometaphase C. metaphase D. prophase E. anaphase

D. prophase

Crossing over occurs during _____. A. metaphase I B. metaphase II C. prophase II D. prophase I

D. prophase I

The exchange of parts between nonhomologous chromosomes is called _____. A. transformation B. inversion C. crossing over D. reciprocal translocation

D. reciprocal translocation