Chapter 13 Review

Key Concepts: • Offspring acquire genes from parents by inheriting chromosomes. • Fertilization and meiosis alternate in sexual life cycles. • Meiosis reduces the number of chromosome sets from diploid to haploid. • Genetic variations produced in sexual life cycles contributes to evolution.
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How many genes are present in the human genome?

a. 23
b. 46
c. hundreds
d. tens of thousands
e. a virtually infinite number
tens of thousands

Each chromosome has hundreds or thousands of genes; the entire human genome has on the order of 20,000 to 25,000 genes.
What is a locus?

a. the precise location of a gene on a chromosome
b. a structure that appears during prophase I and consists of two paired genes
c. the precise DNA sequence of a gene
d. a type of spore made only by fungi
e. a cell with two chromosome sets
the precise location of a gene on a chromosome

The location of a gene within the genome, including the identity of the particular chromosome that it maps to and its specific position on that chromosome, is called its locus.
Sexual and asexual reproduction are alike in that __________.

a. they both give rise to genetically distinct offspring
b. they both involve two parents
c. they both require meiosis to complete the reproductive cycle
d. they can both occur in multicellular organisms
e. in both cases, every parent transmits all of its genes to its progeny
they can both occur in multicellular organisms

Examples of both sexual and asexual reproduction have been observed in multicellular organisms.
A clone is the product of __________.

a. asexual reproduction
b. sexual reproduction
c. mitosis
d. meiosis
e. asexual reproduction and mitosis
f. sexual reproduction and meiosis
asexual reproduction and mitosis

In asexual reproduction, an organism produces genetically identical progeny, or clones, by mitosis.
Unless the chromosomes were stained to show band patterns, a karyotype would be LEAST likely to show which of the following?

a. an extra chromosome
b. a large part of a chromosome duplicated
c. a missing chromosome
d. part of a chromosome turned around
e. the attachment of a large part of a chromosome to another chromosome
part of a chromosome turned around

An inversion, which affects neither the number of chromosomes nor the length of a chromosome, is generally difficult to detect without staining to show chromosomal bands.
A karyotype is __________.

a. the physical traits a person has
b. a method of identifying crossover events
c. all the possible gametes a person could produce
d. a photograph of all the chromosomes in a single cell from an individual
e. a list of all the genes a person carries
a photograph of all the chromosomes in a single cell from an individual

Karyotypes, ordered displays of an individual's chromosomes, are useful in identifying chromosomal abnormalities.
Fertilization produces __________.

a. a haploid zygote in some life cycles and a diploid zygote in others
b. a haploid zygote
c. a diploid zygote
d. a diploid zygote, except during the gametophyte stage of alternation of generations
e. a multicellular haploid organism in a life cycle with an alternation of generations
a diploid zygote

Fertilization always involves the fusion of gametes and produces a diploid zygote.
Which, if any, of the following statements is true?

a. Diploid cells can divide by mitosis.
b. Diploid cells can divide by meiosis.
c. Haploid cells can divide by mitosis.
d. Haploid cells cannot divide by meiosis.
e. All of the above responses are correct.
All of the above responses are correct.

Diploid cells can divide by either mitosis or meiosis, but haploid cells can divide only by mitosis.
Which of the following is part of the life cycle called alternation of generations?

a. multicellular haploid stage (gametophyte)
b. multicellular diploid stage (sporophyte)
c. zygote
d. spores
e. All of the listed responses are correct.
All of the listed responses are correct.

In alternation of generations, zygotes give rise to multicellular, diploid sporophytes, and spores give rise to multicellular, haploid gametophytes.
The sexual cycle of the diploid, multicellular algal genus Fucus involves __________.

a. mitosis only
b. both mitosis and meiosis but not fertilization
c. both mitosis and fertilization but not meiosis
d. only meiosis and fertilization
e. mitosis, meiosis, and fertilization
mitosis, meiosis, and fertilization

All multicellular organisms undergo mitosis, and all diploid, sexually reproducing organisms undergo meiosis and fertilization, which are complementary processes.
A life cycle in which the only multicellular form is haploid is most typical of __________.

a. primates
b. plants
c. fungi
d. prokaryotes
e. fish
fungi

In most fungi, the multicellular form is haploid, and fertilization (and creation of a zygote) is immediately followed by meiosis.
In sexually reproducing species, the chromosome number remains stable over time because __________ and __________ always alternate.

a. meiosis ... fertilization
b. meiosis ... mitosis
c. mitosis ... fertilization
d. meiosis ... interphase
e. meiosis I ... meiosis II
meiosis ... fertilization

Meiosis reduces the number of chromosomes by half, and fertilization restores the number to the diploid state.
The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?

a. 11
b. 22
c. 44
d. 88
e. 132
44

Haploid sex cells contain half as many chromosomes as diploid somatic cells.
In a diploid cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.

a. 0
b. 5
c. 10
d. 20
e. 40
5

Haploid sex cells contain half as many chromosomes as diploid somatic cells.
How many pairs of autosomes do humans have?

a. 23
b. 22
c. 2
d. 1
e. It depends on the sex of the individual.
22

Humans have 22 pairs of autosomes and one pair of sex chromosomes.
Sister chromatids __________.

a. are involved in mitosis only
b. are pairs of chromosomes, one of which comes from the father and one of which comes from the mother
c. are identical copies of each other formed through DNA synthesis
d. have the same gene loci but may have different alleles of some genes
e. are involved in meiosis only
are identical copies of each other formed through DNA synthesis

Sister chromatids are identical and participate in both mitosis and meiosis.
Which of the following statements about homologous chromosomes is correct?

a. They are found in animal cells but not in plant cells.
b. They have genes for the same traits at the same loci.
c. They pair up in prophase II.
d. They are found in haploid cells.
e. They are found in the cells of human females but not in those of human males.
They have genes for the same traits at the same loci.

The chromosomes that make up a pair are called homologous chromosomes, and they carry genes controlling the same inherited characters.
When we say that an organism is haploid, we mean that __________.

a. its cells each have one chromosome
b. it has one half of a chromosome
c. its cells have a single set of chromosomes
d. its cells have two sets of chromosomes
e. its cells have half of one set of chromosomes
its cells have a single set of chromosomes

Many fungi and some protists exist as haploid organisms, and plants and some algae also have a haploid stage (called a gametophyte) as part of the life cycle called alternation of generations.
Which of the following is a function of mitosis in humans?

a. production of eggs
b. production of sperm
c. decreasing the number of chromosomes
d. multiplication of body cells
e. increasing genetic variability
multiplication of body cells

This is a function of mitosis in humans. It is mitosis that enables a multicellular adult to form from a fertilized egg and produces cells for growth and tissue repair.
Somatic cells in humans contain __________ set(s) of chromosomes and are therefore termed __________.

a. one ... diploid
b. two ... haploid
c. one ... haploid
d. two ... diploid
e. three ... triploid
two ... diploid

Somatic cells in interphase contain the characteristic diploid chromosome number.
Nearly all life cycles have both haploid and diploid phases. Usually, the transition from haploid to diploid takes place __________.

a. during crossing over in meiosis
b. when DNA is replicated during the S phase of the cell cycle
c. when mitotic cytokinesis occurs
d. at fertilization, when gametes fuse
e. during embryonic development
at fertilization, when gametes fuse

The union of haploid gametes at fertilization produces the zygote, or fertilized egg, which marks the beginning of the diploid phase of the life cycle.
Spores and gametes are different in that __________.

a. gametes never resemble spores morphologically
b. gametes are always haploid whereas spores are diploid
c. gametes can fuse to form a zygote, but spores can develop into independent organisms without first forming a zygote
d. only the formation of gametes contributes to genetic variation
e. gametes are derived directly from sporophytes to form gametophytes
gametes can fuse to form a zygote, but spores can develop into independent organisms without first forming a zygote

Unlike a gamete, a spore gives rise to a multicellular organism without fusing with another cell.
Humans have 46 chromosomes. This number of chromosomes will be found in __________.

a. all cells in anaphase of mitosis
b. all the egg and sperm cells
c. all gamete-producing cells after meiosis I
d. liver cells
e. all the cells of the body
liver cells

Liver cells are somatic cells, and they contain the characteristic diploid chromosome number.
Which of the following results in cells that contain half the parental chromosome number?

a. cytokinesis
b. mitosis
c. meiosis
d. interphase
e. metaphase
meiosis

The two cell divisions of meiosis, I and II, produce four haploid daughter cells.
At the end of telophase I of meiosis and the first cytokinesis, there are __________.

a. four haploid cells
b. two diploid cells
c. four diploid cells
d. one haploid ovum and three polar bodies
e. two haploid cells
two haploid cells

Each of these cells carries a haploid set of chromosomes, each consisting of two chromatids.
What is the typical result when a diploid cell has completed meiosis?

a. two diploid cells
b. two haploid cells
c. four diploid cells
d. four haploid cells
e. two haploid cells and two diploid cells
four haploid cells

The two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.
Synapsis occurs during __________.

a. anaphase I
b. prophase I
c. cytokinesis
d. prophase II
e. metaphase I
prophase I

Synapsis is the pairing of homologous chromosomes during prophase I.
Which of the following occurs during anaphase II?

a. Homologs separate and migrate toward opposite poles.
b. Sister chromatids separate and migrate toward opposite poles.
c. Nuclei re-form.
d. Chromosomes line up on one plate.
e. The synaptonemal complex disappears.
Sister chromatids separate and migrate toward opposite poles.

This occurs during anaphase II.
Which of the following occurs during anaphase I?

a. Homologs separate and migrate toward opposite poles.
b. Sister chromatids separate and migrate toward opposite poles.
c. Nuclei re-form.
d. Chromosomes line up on one plate.
e. The cell is haploid.
Homologs separate and migrate toward opposite poles.

This occurs during anaphase I.
Cytokinesis is the __________.

a. exchange of homologous regions of nonsister chromatids
b. formation of tetrads
c. independent assortment of chromosomes
d. lining up of tetrads at the metaphase plate
e. division of the cytoplasm to create two cells
division of the cytoplasm to create two cells

Cytokinesis normally accompanies both telophase I and telophase II, as well as the telophase of mitosis.
What is the function of meiosis?

a. to make exact copies of the parent cell
b. to make one cell with twice the number of chromosomes as the parent pairs
c. to make four cells with the same chromosome number as the parent
d. to make cells with a haploid (half that of the parents) number of chromosomes
e. to make diploid spores
to make cells with a haploid (half that of the parents) number of chromosomes

The two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.
Crossing over occurs during __________.

a. cytokinesis
b. metaphase I
c. prophase II
d. metaphase II
e. prophase I
prophase I

Crossing over, resulting in genetic recombination, occurs during synapsis in prophase I.
Regions of chromosomes where nonsister chromatids cross over are called __________.

a. mutations
b. homologs
c. kinetochores
d. chiasmata
e. tetrads
chiasmata

Chiasmata are regions where crossing over has occurred.
The synaptonemal complex __________.

a. physically connects homologous chromosomes during prophase I
b. physically connects homologous chromosomes during mitosis
c. is broken down by enzymes during anaphase II
d. is another name for chiasmata
e. is formed by a protein called cohesin
physically connects homologous chromosomes during prophase I

The synaptonemal complex helps to line up homologous chromosomes gene by gene.
An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis?

a. 2
b. 3
c. 4
d. 8
e. 16
4

Because of the synapsis of homologous chromosomes, the number of tetrads in meiosis I will be the same as the haploid number of chromosomes.
Which event occurs only during prophase I of the first meiotic division?

a. Homologous chromosomes line up at the center of the cell.
b. Synapsis of homologous pairs occurs.
c. The nuclear membrane breaks down.
d. Replication of DNA takes place.
e. A spindle of microtubules forms.
Synapsis of homologous pairs occurs.

Synapsis of homologous chromosomes occurs at prophase of meiosis I.
Which of the following occurs in meiosis, but NOT mitosis?

a. The cells formed have the same combination of genes as found in the initial cell.
b. Homologous chromosomes separate.
c. The nuclear envelope disappears.
d. Sister chromatids separate and move to opposite ends of the spindle.
e. A spindle apparatus forms.
Homologous chromosomes separate.

Homologous chromosomes separate during anaphase I; this is the event that produces haploid cells.
Which function makes meiosis lengthier and more complex than mitosis?

a. decreasing the chromosome number to haploid
b. introducing genetic variation among the daughter cells
c. ensuring that each daughter cell gets a single, complete set of chromosomes
d. undergoing two rounds of cytokinesis
e. All of the listed responses are correct.
All of the listed responses are correct.

Meiosis involves two divisions that typically result in four daughter cells (instead of two). Each cell has half the number of chromosomes of the original parent cell, and is, of course, not genetically identical to the parent cell.
Ignoring crossover events, how many kinds of gametes can be produced by an organism with a diploid number of 8?

a. 2
b. 4
c. 8
d. 16
e. 32
16

The number of combinations possible when chromosomes assort independently into gametes during meiosis is 2n, where n is the haploid number of chromosomes.
Which of the following contributes to genetic variation in sexually reproducing species?

a. crossing over, internal fertilization, independent assortment
b. independent assortment, spindle formation, random fertilization
c. random fertilization, DNA synthesis, independent assortment
d. random fertilization, independent assortment, crossing over
e. internal fertilization, spindle formation, crossing over
random fertilization, independent assortment, crossing over

These three aspects of sexual reproduction increase genetic variation.
In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing __________ different types of gametes.

a. 232
b. 1 million
c. 223
d. 24
e. 100,000
223

For each gamete there are two possibilities for each chromosome (the paternal or the maternal chromosome), and there are 23 different chromosomes per gamete.
The diploid number of chromosomes in a certain animal is 8 (2n = 8). How do the four pairs of homologous chromosomes align and separate during meiosis?

a. All of the maternal chromosomes always move to one pole, and all the paternal chromosomes always move to the other pole.
b. All 16 chromatids move together.
c. Exactly two maternal and two paternal chromosomes always move to each of the two poles.
d. The first to move influences all the others.
e. They align and assort independently to form any of 16 different combinations.
They align and assort independently to form any of 16 different combinations.

Because each pair of homologous chromosomes is positioned independently in metaphase I, the first meiotic division results in the independent assortment of paternal and maternal chromosomes into daughter cells. In a case in which 2n = 8, 16 combinations of chromosomes are possible for gametes.
In a diploid set of chromosomes, one member of each pair of homologous chromosomes is derived from the father (paternal), and the other comes from the mother (maternal). If 2n = 6, what is the probability that a particular gamete will contain only paternal chromosomes?

a. 1/4
b. 1/8
c. 1/16
d. 1/32
e. The answer cannot be determined from these data.
1/8

The chance of any one paternal chromosome ending up in a particular gamete is 1/2, so the chance that all three would be of paternal origin would be (1/2)n, where n = 3.
The major contribution of sex to evolution is that __________.

a. it is the only mechanism for species to reproduce
b. it provides a method to increase genetic variation
c. it provides a way in which somatic mutations can be inherited
d. it is the only mechanism for species to reproduce and it provides a method to increase genetic variation
e. it provides a method to increase genetic variation and it provides a way in which somatic mutations can be inherited
it provides a method to increase genetic variation

Sexual life cycles produce enormous genetic variation among offspring.
Which of the following answers is NEITHER involved with crossing over NOR an outcome of crossing over?

a. The DNA in two nonsister chromatids is broken by specific proteins at exact points.
b. Chiasmata indicate where crossing over is occurring between homologs.
c. the random alignment of homologous pairs of chromosomes at metaphase I
d. formation of chromosomes containing paternal and maternal alleles
e. All of the listed responses pertain to the process of crossing over.
the random alignment of homologous pairs of chromosomes at metaphase I

This process is not related to crossing over but is an outcome of independent assortment.
Which of the following statements reflects an advantage that sexual reproduction likely provides over asexual reproduction?

a. In terms of energetic costs, sexual reproduction is a cheaper strategy than asexual reproduction for generating genetic variation in a population.
b. Although sexual and asexual reproduction both offer opportunities for increasing genetic variation, sexual reproduction is comparatively lower in its energetic costs to the organism.
c. Although energetically more costly than asexual reproduction, sexual reproduction leads to different combinations of alleles that could provide adaptability in a changing environment.
d. Sexual reproduction maintains the same combination of alleles and does not run the risk of losing successful combinations of alleles as is observed to occur in asexually reproducing organisms.
e. Although both reproductive strategies perpetuate the same combination of alleles within individuals in a population, sexual reproduction is energetically less costly than asexual reproduction.
Although energetically more costly than asexual reproduction, sexual reproduction leads to different combinations of alleles that could provide adaptability in a changing environment.

Asexual reproduction is energetically cheaper than sexual reproduction but perpetuates the same combination of alleles in individuals over generations; thus, it does not provide the capacity for adaptation as do sexually reproducing organisms.
Although __________ is nearly universal among animals, bdelloid rotifers __________.

a. asexual reproduction ... have achieved great diversity by using sexual reproduction
b. sexual reproduction ... reproduce asexually and achieve genetic diversity by mutations alone
c. sexual reproduction ... reproduce asexually because they inhabit very stable environments and the production of gametes would be an inefficient use of energy
d. sexual reproduction ... reproduce asexually but can increase genetic variation present in a population by means of the uptake of DNA from other rotifers
sexual reproduction ... reproduce asexually but can increase genetic variation present in a population by means of the uptake of DNA from other rotifers

Although bdelloid rotifers are incapable of sexual reproduction, they can carry out a form of "horizontal gene transfer" in which they take up DNA from the environment and incorporate it into their genome. This adaptation demonstrates that asexually reproducing animals are not limited to mutation alone in generating genetic diversity in a population.
A human cell containing 22 autosomes and a Y chromosome is

a. a sperm.
b. a somatic cell of a female.
c. a zygote.
d. an egg.
e. a somatic cell of a male.
a sperm
Homologous chromosomes move toward opposite poles of a dividing cell during

a. binary fission.
b. meiosis I.
c. mitosis.
d. fertilization.
e. meiosis II.
meiosis I
Meiosis II is similar to mitosis in that

a. sister chromatids separate during anaphase.
b. homologous chromosomes synapse.
c. the chromosome number is reduced.
d. DNA replicates before the division.
e. the daughter cells are diploid.
sister chromatids separate during anaphase
If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be

a. 0.25x.
b. 0.5x.
c. x.
d. 2x.
e. 4x.
2x
If we continued to follow the cell lineage from question 4, then the DNA content of a single cell at metaphase of meiosis II would be

a. 0.25x.
b. 0.5x.
c. x.
d. 2x.
e. 4x.
x
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