Chapter 13 Practice Test

Ignoring crossover events, how many kinds of gametes can be produced by an organism with a diploid number of 8?

16 (The number of combinations possible when chromosomes assort independently into gametes during meiosis is 2n, where n is the haploid number of chromosomes).

How many pairs of autosomes do humans have?

22 (Humans have 22 pairs of autosomes and one pair of sex chromosomes).

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

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).

What is the typical result when a diploid cell has completed meiosis?

4 haploid daughter 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).

In a diploid cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.

5 (Haploid sex cells contain half as many chromosomes as diploid somatic cells).

Somatic cells in humans contain ___#_______ set(s) of chromosomes and are therefore termed __________.

two ... diploid (Somatic cells in interphase contain the characteristic diploid chromosome number).

At the end of telophase I of meiosis and the first cytokinesis, there are __________.

two haploid cells (Each of these cells carries a haploid set of chromosomes, each consisting of two chromatids).

Sister chromatids are

identical copies of each other formed through DNA synthesis (both participate in meiosis & mitosis).

The major contribution of sex to evolution is that __________.

it provides a method to increase genetic variation

When we say that an organism is haploid, we mean that __________.

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.)

How many genes are present in the human genome?

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.

Genome

the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes

What is a locus?

the precise location of a gene on a chromosome

What is the function of meiosis?

to make cells with a haploid (half that of the parents) number of chromosomes

Meiosis involves the creation of haploid cells from diploid cells. The haploid chromosome number is created when _____. A) homologous chromosomes separate B) the S phase of the cell cycle is bypassed during meiotic interphase C) sister chromatids separate D) ova and sperm go through their respective maturation processes

A) homologous chromosomes separate

Crossing over occurs during

Prophase I

Synapsis occurs during _____.

Prophase I

True or False. Species that have more recent common ancestors should have less homologous traits in common.

False

A life cycle in which the only multicellular form is haploid is most typical of __________.

Fungi (In most fungi, the multicellular form is haploid, and fertilization (and creation of a zygote) is immediately followed by meiosis.)

What occurs during anaphase I?

Homologs separate and migrate toward opposite poles.

What occurs during anaphase II?

Sister chromatids separate and migrate toward opposite poles.

Which of the following occurs in meiosis, but NOT mitosis? a.)Homologous chromosomes separate. b.)A spindle apparatus forms. c.)The cells formed have the same combination of genes as found in the initial cell. d.)Sister chromatids separate and move to opposite ends of the spindle. e.)The nuclear envelope disappears.

a.)Homologous chromosomes separate (this is the event that produces haploid cells.)

Which of the following occurs during anaphase II? a.)Sister chromatids separate and migrate toward opposite poles. b.)Nuclei re-form. c.)Homologs separate and migrate toward opposite poles. d.)The synaptonemal complex disappears. e.)Chromosomes line up on one plate.

a.)Sister chromatids separate and migrate toward opposite poles.

Which of the following answers is NEITHER involved with crossing over NOR an outcome of crossing over? a.)the random alignment of homologous pairs of chromosomes at metaphase I b.)Chiasmata indicate where crossing over is occurring between homologs. c.)formation of chromosomes containing paternal and maternal alleles d.)The DNA in two non-sister chromatids is broken by specific proteins at exact points. e.)All of the listed responses pertain to the process of crossing over.

a.)the random alignment of homologous pairs of chromosomes at metaphase I (outcome of independent assortment)

Centromeres split and sister chromosomes migrate to opposite poles in _____.

anaphase II

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

b.)a diploid zygote

The synaptonemal complex __________. a.)is formed by a protein called Cohesion b.)physically connects homologous chromosomes during prophase I c.)is broken down by enzymes during anaphase II d.)physically connects homologous chromosomes during mitosis is another name for chiasmata

b.)physically connects homologous chromosomes during prophase I (helps to line up homologous chromosomes gene by gene).

Which of the following contributes to genetic variation in sexually reproducing species? a.)internal fertilization, spindle formation, crossing over b.)random fertilization, independent assortment, crossing over c.)crossing over, internal fertilization, independent assortment d.)random fertilization, DNA synthesis, independent assortment e.)independent assortment, spindle formation, random fertilization

b.)random fertilization, independent assortment, crossing over

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

c.)44

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

c.)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).

Which of the following statements about homologous chromosomes is correct? a.)They are found in haploid cells. b.)They pair up in prophase II. c.)They have genes for the same traits at the same loci. d.)They are found in animal cells but not in plant cells. e.)They are found in the cells of human females but not in those of human males.

c.)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).

The sexual cycle of the diploid, multicellular algal genus Fucus involves __________. a.)both mitosis and fertilization but not meiosis b.)both mitosis and meiosis but not fertilization c.)mitosis, meiosis, and fertilization d.)only meiosis and fertilization e.)mitosis only

c.)mitosis, meiosis, and fertilization (All multicellular organisms undergo mitosis, and all diploid, sexually reproducing organisms undergo meiosis and fertilization, which are complementary processes).

Regions of chromosomes where non-sister chromatids cross over are called __________.

chiasmata

Cytokinesis is a division of the _______

cytoplasm to create two cells (Cytokinesis normally accompanies both telophase I and telophase II, as well as the telophase of mitosis).

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

d.)a photograph of all the chromosomes in a single cell from an individual

In sexually reproducing species, the chromosome number remains stable over time because __________ and __________ always alternate. a.)meiosis I ... meiosis II b.)mitosis ... fertilization c.)meiosis ... mitosis d.)meiosis ... fertilization e.)meiosis ... interphase

d.)meiosis ... fertilization (Meiosis reduces the number of chromosomes by half, and fertilization restores the number to the diploid state.)

Sexual and asexual reproduction are alike in that __________. a.) n both cases, every parent transmits all of its genes to its progeny b.)they both involve two parents c.)they both give rise to genetically distinct offspring d.)they can both occur in multicellular organisms e.)they both require meiosis to complete the reproductive cycle

d.)they can both occur in multicellular organisms

Which, if any, of the following statements is true? a.)Haploid cells cannot divide by meiosis. b.)Haploid cells can divide by mitosis. c.)Diploid cells can divide by mitosis. d.)Diploid cells can divide by meiosis. e.)All of the above responses are correct.

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

e.)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; plants undergo this)

Which function makes meiosis lengthier and more complex than mitosis? a.)ensuring that each daughter cell gets a single, complete set of chromosomes b.)undergoing two rounds of cytokinesis c.)introducing genetic variation among the daughter cells d.)decreasing the chromosome number to haploid e.)All of the listed responses are correct.

e.)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).

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 mitotic cytokinesis occurs c.)during embryonic development d.)when DNA is replicated during the S phase of the cell cycle e.)at fertilization, when gametes fuse

e.)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).

Which of the following is a function of mitosis in humans? a.)increasing genetic variability b.)production of eggs c.)production of sperm d.)decreasing the number of chromosomes e.)multiplication of body cells

e.)multiplication of body cells (It is mitosis that enables a multicellular adult to form from a fertilized egg and produces cells for growth and tissue repair).