Biology Chapter 13:

How many genes are present in the human genome?

tens of thousands

Synapsis occurs during _____.

prophase I

Which of the following statements about homologous chromosomes is correct?

They have genes for the same traits at the same loci.

Regions of chromosomes where nonsister chromatids cross over are called __________.

chiasmata

Although __________ is nearly universal among animals, bdelloid rotifers __________.

sexual reproduction ... reproduce asexually but can increase genetic variation present in a population by means of the uptake of DNA from other rotifers

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?

1/8

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.

16

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

16

How many pairs of autosomes do humans have?

22

In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing __________ different types of gametes

223

Normal human gametes carry _____ chromosomes.

23 This is the number of chromosomes in a single set of human chromosomes.

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

2x.

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

4

The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?

44

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

5

Which of the following statements reflects an advantage that sexual reproduction likely provides over 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.

Two sister chromatids are joined at the centromere prior to meiosis. Which statement is correct?

Barring mutation, the two sister chromatids must be identical.

Which, if any, of the following statements is true?

Diploid cells can divide by mitosis. Diploid cells can divide by meiosis. Haploid cells can divide by mitosis. Haploid cells cannot divide by meiosis.

Identify all possible products of meiosis in plant and animal life cycles.

Gametes (sperm and eggs) and Spores In most animal life cycles, the products of meiosis are gametes. However, in plants, the products of meiosis are spores.

How are sister chromatids and homologous chromosomes different from each other?

Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication. One homologous chromosome comes from the father, and the other comes from the mother. Sister chromatids are identical copies of each other.

Which of the following occurs in meiosis, but NOT mitosis?

Homologous chromosomes separate.

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 event occurs only during prophase I of the first meiotic division?

Synapsis of homologous pairs occurs.

What is the best evidence telling you whether this cell is diploid or haploid?

The cell is diploid because it contains two sets of chromosomes. This cell contains two copies of each chromosome, one from the male parent and the other from the female parent, making it diploid.

This chromosome has two chromatids, joined at the centromere. What process led to the formation of the two chromatids?

The two chromatids were formed by duplication of a chromosome.

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?

They align and assort independently to form any of 16 different combinations.

Fertilization produces __________.

a diploid zygote

A karyotype is __________.

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

A human cell containing 22 autosomes and a Y chromosome is

a sperm.

Homologous chromosomes migrate to opposite poles during _____.

anaphase I During anaphase I sister chromatids remain attached at their centromeres, and homologous chromosomes move to opposite poles.

During _____ sister chromatids separate.

anaphase II Anaphase II is essentially the same as mitotic anaphase except that the cell is haploid.

Sister chromatids __________.

are identical copies of each other formed through DNA synthesis

A clone is the product of __________.

asexual reproduction and mitosis

Nearly all life cycles have both haploid and diploid phases. Usually, the transition from haploid to diploid takes place __________.

at fertilization, when gametes fuse

Which function makes meiosis lengthier and more complex than mitosis?

decreasing the chromosome number to haploid introducing genetic variation among the daughter cells ensuring that each daughter cell gets a single, complete set of chromosomes undergoing two rounds of cytokinesis

Cytokinesis is the __________.

division of the cytoplasm to create two cells

Heritable variation is required for which of the following?

evolution

Meiosis II typically produces _____ cells, each of which is _____.

four ... haploid At the end of meiosis II there are typically 4 haploid cells.

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

four haploid cells

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

fungi

Spores and gametes are different in that __________.

gametes can fuse to form a zygote, but spores can develop into independent organisms without first forming a zygote

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

Humans have 46 chromosomes. This number of chromosomes will be found in __________.

liver cells

What results in cells that contain half the parental chromosome number?

meiosis

Human gametes are produced by _____.

meiosis Meiosis produces haploid gametes from a diploid parental cell.

In sexually reproducing species, the chromosome number remains stable over time because __________ and __________ always alternate.

meiosis ... fertilization

Homologous chromosomes move toward opposite poles of a dividing cell during

meiosis I.

During _____ chromosomes align single file along the equator of a haploid cell.

metaphase II Metaphase II is essentially the same as mitotic metaphase except that the cell is haploid.

The sexual cycle of the diploid, multicellular algal genus Fucus involves __________.

mitosis, meiosis, and fertilization

Which of the following is part of the life cycle called alternation of generations?

multicellular haploid stage (gametophyte) multicellular diploid stage (sporophyte) zygote spores

Which of the following is a function of mitosis in humans?

multiplication of body cells

Unless the chromosomes were stained to show band patterns, a karyotype would be LEAST likely to show which of the following?

part of a chromosome turned around

The synaptonemal complex __________.

physically connects homologous chromosomes during prophase I

Crossing over occurs during __________.

prophase I

Synapsis occurs during __________.

prophase I

During _____ a spindle forms in a haploid cell.

prophase II

Which of the following contributes to genetic variation in sexually reproducing species?

random fertilization, independent assortment, crossing over

Meiosis II is similar to mitosis in that

sister chromatids separate during anaphase

Meiosis II is similar to mitosis in that

sister chromatids separate during anaphase.

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

telophase I At the end of telophase I and cytokinesis, there are two haploid cells with chromosomes that consist of two sister chromatids each.

At the end of _____ and cytokinesis there are four haploid cells.

telophase II

What is crossing over?

the exchange of homologous portions of nonsister chromatids The result is new combinations of genetic material (genetic recombination).

What is synapsis?

the pairing of homologous chromosomes occurs in prophase I

What is a locus?

the precise location of a gene on a chromosome

Which of the following answers is NEITHER involved with crossing over NOR an outcome of crossing over?

the random alignment of homologous pairs of chromosomes at metaphase I

Sexual and asexual reproduction are alike in that __________.

they can both occur in multicellular organisms

What is the function of meiosis?

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

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

two ... diploid

Meiosis I produces _____ cells, each of which is _____.

two ... haploid At the end of meiosis I there are two haploid cells.

Mitosis results in the formation of how many cells; meiosis results in the formation of how many cells?

two diploid cells ... four haploid cells In mitosis a cell that has doubled its genetic material divides to produce two diploid daughter cells. In meiosis a cell that has doubled its genetic material undergoes two rounds of division, producing four haploid cells.

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

two haploid cells

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

x.