Chapter 8 Mastering Biology – Flashcards

The creation of genetically identical offspring by a single parent, without the participation of sperm and egg, is called -sexual reproduction. -spontaneous generation. -asexual reproduction. -regeneration.

Which of the following statements regarding sexual and asexual reproduction is true? -Sexual reproduction is more likely to increase genetic variation than is asexual reproduction. -Only offspring from asexual reproduction inherit traits from two parents. -Cell division only occurs after sexual reproduction. -Sexual reproduction typically includes the development of unfertilized eggs.

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

Asexual reproduction requires ________ individual(s). 1 2 0 3

With the exception of identical twins, siblings who have the same two biological parents are likely to look similar, but not identical, to each other because they have -the same combination of traits, but different genes. -identical chromosomes, but different genes. -identical genes but different chromosomes. -a similar but not identical combination of genes.

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

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

Eukaryotic chromosomes differ from prokaryotic chromosomes in that they -are circular in structure. -are simpler. -include fewer proteins. -are housed in a membrane-enclosed nucleus.

Which of the following helps maintain the structure of chromosomes and control the activity of genes? -ribosomes -proteins -the nuclear membrane -centromeres

Sister chromatids are -joined together at a centromere. -unique to prokaryotes. -made only of DNA. -found right after a cell divides.

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

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? -It causes the cell to elongate. -It ensures the separation of the replicated chromosomes as new membrane is made. -It ensures the formation of two complete nuclei around each of the chromosomes. -This keeps the separate chromosomes together.

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

Which of the following statements regarding prokaryotes is false? -Prokaryotic cells are generally smaller and simpler than eukaryotic cells. -Prokaryotic chromosomes are more complex than those of eukaryotes. -In prokaryotes, daughter chromosomes are separated by an active movement away from each other and the growth of a new plasma membrane between them. -Most prokaryotes reproduce by binary fission

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

What must happen before a cell can begin mitosis? -The nucleus must divide in two. -The sister chromatids must be separated. -A mitotic spindle must form. -The nuclear envelope must break up. -The chromosomes must be duplicated.

The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis? -Interphase -Prophase -Anaphase -Telophase -Metaphase

The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis? -Metaphase -Prophase -Telophase -Anaphase -Interphase

The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis? -Interphase -Anaphase -Telophase -Prophase -Metaphase

At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________. -cytokenesis -meiosis -condensation -replication -telophase

The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis? -Interphase -Prophase -Anaphase -Telophase -Metaphase

Eukaryotic cells spend most of their cell cycle in which phase? telophase metaphase prophase interphase

Which of the following occurs during interphase? -separation of newly formed DNA to opposite ends of the cell -cell growth and duplication of the chromosomes -a reduction in the size of the nuclear membrane -cytokinesis

The genetic material is duplicated during the mitotic phase. the S phase. G1. G2.

The process by which the cytoplasm of a eukaryotic cell divides to produce two cells is called telophase. mitosis. cytokinesis. binary fission.

Looking into your microscope, you spot an unusual cell. Instead of the typical rounded cell shape, the cell has a very narrow middle separating two bulging ends. It sort of looks like the number 8! Then you realize that this cell is about to undergo mitosis. in the G1 phase of interphase. in the S phase of interphase. undergoing cytokinesis.

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

The phase of mitosis during which the mitotic spindle begins to form is interphase. prophase. anaphase. metaphase.

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

At the start of mitotic anaphase, -the centromeres of each chromosome come apart. -nuclear envelopes begin to form around the chromosomes. -equivalent and complete collections of chromosomes have reached the two poles. -the chromatid DNA replicates.

During which phase of mitosis does the nuclear envelope re-form? metaphase anaphase telophase prophase

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

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

Which of the following is a feature of plant cell division that distinguishes it from animal cell division? -formation of a cleavage furrow -production of four (rather than two) new cells per mitotic division -lack of cytokinesis -formation of a cell plate

Which of the following features likely accounts for the difference between plant and animal cell cytokinesis? -Animal cells lack chloroplasts. -Plant cells have cell walls. -Plant cells have two sets of chromosomes; animal cells have one set of chromosomes. -Animal cells lack the microfilaments required for forming a cleavage furrow.

What type of cell is shown? plant cell in metaphase plant cell in telophase animal cell in metaphase animal cell in telophase

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? -alignment of eukaryotic chromosomes at the metaphase plate -cytokinesis in an animal cell -cytokinesis in a plant cell -separation of eukaryotic chromosomes at anaphase

Which of the following must occur for a plant or animal to grow and develop normally? -Sufficient light must be available to stimulate cell division. -Sufficient oxygen must be available to stimulate cell division. -The organism must receive a supply of the appropriate hormones from its parents. -The organism must be able to control the timing and rate of cell division in different parts of its body.

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 cell division repression. cell constraint. growth factor desensitization. density-dependent inhibition.

As a patch of scraped skin heals, the cells fill in the injured area but do not grow beyond that. This is an example of growth factor inhibition. density-dependent inhibition. density-independent inhibition. anchorage independence.

Which of the following is probably the main factor responsible for the phenomenon of density-dependent inhibition? -a local accumulation of growth-inhibiting factors -cells' innate ability to "sense" when the organ of which they are a part has no need for additional cells -physical contact of cell-surface proteins between adjacent cells -a local deficiency of nutrients

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? -Cancer cells continue to die at a rate that is equal to their growth. -Cancer cells have inactive receptors for growth factors. -Cancer cells continuously secrete growth factors into the cell culture medium. -Cancer cells are unable to attach to a surface and grow.

Meiosis starts with a single diploid cell and produces two haploid cells. four diploid cells. four haploid cells. two diploid cells. eight haploid cells.

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

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

The correct order of events during meiosis is -prophase I, anaphase I, metaphase I, telophase I, meiosis II, cytokinesis. -metaphase I, prophase I, anaphase I, telophase I, cytokinesis, meiosis II. -metaphase I, prophase I, telophase I, anaphase I, cytokinesis, meiosis II. -prophase I, anaphase I, telophase I, metaphase I, meiosis II. -prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.

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? prophase I. meiosis II. telophase I. anaphase I. Metaphase I.

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

A pair of sex chromosomes found in a human male is most like a bride and groom. a knife, fork, and spoon. identical twins. a pair of blue jeans.

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

Which of the following statements regarding the function of mitosis is false? -Mitosis allows organisms to generate genetic diversity. -Mitosis allows organisms to repair tissues. -Mitosis allows organisms to reproduce asexually. -Mitosis allows organisms to grow.

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

Which of the following statements regarding mitosis and meiosis is false? -All sexual life cycles involve an alternation of diploid and haploid stages. -A normal human zygote has 46 chromosomes. -Meiosis only occurs in the ovaries and testes. -Mitosis produces daughter cells with half the number of chromosomes as the parent cell.

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

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? 64 32 16 8

Which of the following statements regarding the differences between mitosis and meiosis is false? -Crossing over is a phenomenon that creates genetic diversity during mitosis. -In meiosis four daughter cells are produced, whereas in mitosis two daughter cells are produced. -Cells produced by mitosis are diploid, whereas cells produced by meiosis are haploid. -In mitosis cytokinesis occurs once, whereas in meiosis cytokinesis occurs twice.

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

Both mitosis and meiosis are preceded by prometaphase. interphase. telophase. prophase.

The M phase of mitosis and M phase of meiosis both occur after interphase. However, the two processes differ in the arrangement and behavior of their chromosomes. How? -The pairing up of homologous chromosomes and crossing over only occur during meiosis. -Homologous chromosomes pair up in mitosis, but not in meiosis. -The centromeres of all chromosomes align on the metaphase plate in meiosis and on opposite sides of the metaphase plate in mitosis. -In meiosis, homologous chromosomes do not cross over; in mitosis, they do.

During which stage of meiosis do synapsis and crossing over occur? metaphase I prophase II prophase I interphase I

Which of the following options correctly describes the behavior of a tetrad during anaphase I of meiosis? -It goes intact to one pole of the dividing cell. -It splits into two pairs of homologous, nonsister chromatids, and one pair goes to each pole of the dividing cell. -It splits into two pairs of sister chromatids, and one pair goes to each pole of the dividing cell. -It splits into four chromosomes, which distribute in random pairs to the two poles of the dividing cell.

At the conclusion of meiosis I, the daughter cells are _____. haploid and the tetrads are still joined haploid and the sister chromatids are joined diploid and the tetrads have separated diploid and the sister chromatids have separated

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

Independent orientation of chromosomes at metaphase I and random fertilization are most like shuffling cards and dealing out hands of poker. alphabetizing files in a filing cabinet. pairing up similar socks after washing your clothes. cutting up a pie into eight even-sized slices.

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

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? 8 6 8 million 64

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

At a chiasma, two ________ are attached to each other. daughter cells non-homologous chromosomes homologous or sister chromatids homologous or non-sister chromatids

Without crossing over -genetic recombination could not occur. -meiosis could not produce haploid gametes. -only a small number of unique gametes could be produced by a single individual. -cells could not complete meiosis.

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

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? one eight four two

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? 1 million 20 1 trillion 1

Karyotyping -reveals the presence of cancerous genes. -shows chromosomes as they appear in metaphase of meiosis II. -examines points of crossing over. -can reveal alterations in chromosome number.

A karyotype is most like -a movie showing the stages of the reproductive cycle of a beetle. -photographs of every couple at a high school prom. -the answer key to a multiple-choice exam. -a map showing the hidden location of buried treasure.

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

Which of the following statements regarding Down syndrome is false? -Down syndrome is least likely to be seen in the infants of mothers over 40. -Down syndrome is the most common serious birth defect in the United States. -People with Down syndrome usually have a shorter life span than normal. -Trisomy 21 is the cause of Down syndrome.

According to the graph, at what maternal age does the incidence of Down syndrome begin to increase substantially? -about 31 or 32 -about 26 or 27 -about 37 or 38 -about 42 or 43

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? -Trisomy for these other autosomal chromosomes occurs so rarely that it has never been documented. -These autosomal chromosomes do not contain the same type of DNA or protein that makes up chromosomes susceptible to trisomy. -Trisomy for these autosomal chromosomes has no effect and therefore would never be noticed. -Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

Nondisjunction occurs when -an entire pair of chromosomes is lost during meiosis I. -a portion of a chromosome breaks off and is lost. -members of a chromosome pair fail to separate. -two chromosomes fuse into one.

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? -All four embryos will be trisomic for chromosome 18. -Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18. -Two of the embryos will be normal, and two will contain a single copy of chromosome 18. -Two of the embryos will be trisomic for chromosome 18, and two will be normal.

Which of the following types of organisms commonly demonstrates polyploidy? fish reptiles mammals flowering plants

How many generations does it take to develop a new plant species by polyploidy? two about twenty one ten

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 _____. 11 23 22 44

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

During binary fission, one copy of the duplicating chromosome moves to the opposite end of the cell. What does this achieve? This keeps the separate chromosomes together. It causes the cell to elongate. It ensures the formation of two complete nuclei around each of the chromosomes. It ensures that each daughter cell receives one copy of the chromosome.

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

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? G1, G2, S, M G1, M, G2, S, G1 S, G1, G2, M G1, S, G2, M

Which of the following shows mitosis in the correct chronological order? -prometaphase, metaphase, prophase, telophase, anaphase -anaphase, prometaphase, metaphase, prophase, telophase -prophase, prometaphase, metaphase, anaphase, telophase -telophase, prophase, anaphase, prometaphase, metaphase

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

Benign tumors differ from malignant tumors in that the cells of a benign tumor _____. -migrate from their initial site to other organs or tissues -have an unusual number of chromosomes -remain confined to their original site - can divide indefinitely if an adequate supply of nutrients is available

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

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

Meiosis differs from mitosis in that _____ only occurs in meiosis. the fragmentation of the nuclear envelope cytokinesis crossing over the formation of a spindle

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

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

During asexual reproduction, yeast cells can produce _____. genetically identical offspring gametes with the same number of chromosomes as the parent cell gametes with only half as many chromosomes as the parent cell two non-identical offspring

The term binary fission is best applied to _____. prokaryotes mitosis plants nuclear chemistry

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

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

Individual chromosomes are usually observed with a light microscope during mitosis, even though cells spend more time in interphase. This is because _____. the DNA has not been replicated yet they leave the nucleus and are dispersed to other parts of the cell they have uncoiled to form long, thin strands sister chromatids do not pair up until division starts

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

A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA in one of the grasshopper daughter cells? 50 units 400 units 200 units 100 units

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

Chromatids form _____. at the start of mitosis during the S phase during G1 during G2

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

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

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

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

One event occurring during prophase is _____. the alignment of chromosomes in a single plane the synthesis of a new nuclear envelope cytokinesis the beginning of the formation of the mitotic spindle

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

Which of the following is a correct representation of an event that occurs in mitosis? -metaphase - chromosomes line up on the equatorial plane. -prophase - chromosomes uncoil. -anaphase - the nuclear envelope disappears. -prometaphase - there is movement of the chromosomes to the poles.

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

At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell? anaphase metaphase prophase telophase

The kinetochores are _____. -sites at which microtubules attach to chromosomes -found as each spindle interlocks at the cell's equator and then moves apart, causing the cell to elongate -the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis -located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers

In some organisms such as certain fungi and algae, cells undergo mitosis repeatedly without subsequently undergoing cytokinesis. What would be the consequence of this? -a decrease in chromosome number -an inability to duplicate DNA -division of the organism into many cells, most lacking nuclei -large cells containing many nuclei

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

Consider the photograph shown below. You can determine this is a plant cell rather than an animal cell because it has _____. formed a cell plate formed a cleavage furrow microtubules separated duplicated chromosomes during mitosis

Cytochalasin B is a chemical that disrupts microfilament formation. This chemical would interfere with _____. formation of a cleavage furrow formation of the mitotic spindle formation of the cell plate DNA replication

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

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

Consider the cell cycle shown below. Cells will usually divide if they receive the proper signal at a checkpoint in the _____ phase of the cell cycle. M G1 S G2

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

Observations of cancer cells in culture support the hypothesis that cancer cells _____. do not exhibit density-dependent inhibition exhibit anchorage dependence produce molecules that inhibit the growth factors required for cell division divide in a controlled manner

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

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

Which of the following is a normal human female? XXY XX X XXX

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

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

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

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

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

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

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

What is the typical result when a diploid cell undergoes meiosis? four diploid cells two diploid cells four haploid cells two haploid cells

In a cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing _____ chromosomes. 5 10 40 20

At the end of telophase I of meiosis, as cytokinesis occurs, there are _____. four haploid cells two haploid cells two diploid cells one haploid ovum and three polar bodies

Synapsis occurs during _____. prophase II telophase I anaphase I prophase I

During anaphase II, _____. -the cell is diploid -sister chromatids separate and migrate toward opposite poles -nuclear membranes re-form -homologues separate and migrate toward opposite poles

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

Crossing over occurs during _____. prophase II metaphase II metaphase I prophase I

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

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

The function of meiosis is to make _____. four cells with the same chromosome number as the parent cell one cell with twice the number of chromosomes as the parent cell exact copies of the parent cell four cells with a haploid number of chromosomes

Which of the following is a key difference between meiosis and mitosis? Synapsis occurs. Chromosomes align at the metaphase plate. Chromosomes condense. Chromosomes migrate to opposite poles.

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

Variation occurs when chromosomes are shuffled in _____. meiosis genetic drift mutation mitosis

In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing _____ different gametes. 46^2 22^3 23^2 1 million

If the diploid number of chromosomes in a certain animal is 6 (2n = 6), there are three sets of two homologous chromosomes each, or three pairs. How do these three pairs align and separate in meiosis? -All 12 chromatids move together. -Any two sister chromatids move together in meiosis II. -All members of each set move together. -They align and assort independently to form any of eight different combinations.

In the picture below, the chromosomal region where the nonsister chromatids are crossing over is called a(n) _____. kinetochore homologue chiasma inversion

Crossing over occurs during _____. anaphase I metaphase I prophase II prophase I

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

Unless the chromosomes were stained to show band patterns, a karyotype would usually be unable to show _____. an inversion a large part of a chromosome duplicated an extra chromosome a missing chromosome

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

Each cell in an individual with Down syndrome contains _____ chromosomes. 24 47 46 45

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

Down syndrome can be the result of _____. deletion of chromosome 21 nondisjunction of chromosome 21 during meiosis a deletion in chromosome 21 occurrence of meiosis without cytokinesis

Which of the following indicates Turner syndrome? XYY XXY XXX XO

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

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 reciprocal translocation a deletion an inversion a nondisjunction

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