Test 4 Review 2

Question 1

Human gametes are produced by ____

Answer 1

Meiosis produces haploid gametes from a diploid parental cell.

Question 2

Normal human gametes carry _____ chromosomes

Answer 2

23

Question 3

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

Answer 3

16 is half of 32.

Question 4

Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?

Answer 4

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.

Question 5

Which of these cells is (are) haploid?

Answer 5

After Meiosis I and Meiosis II (C &D)

Question 6

Crossing Over

Answer 6

Pairing of homologous chromosomes is followed by crossing over, the exchange of genetic material between nonsister chromatids of homologous chromosomes.

Question 7

Recombinant Chromosomes

Answer 7

A chromosome created when crossing over combines the DNA from two parents into a single chromosome.

Each of the chromosomes in gametes B and C are composed of material derived from both parents.

Question 8

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

Answer 8

two, haploid

Question 9

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

Answer 9

four, haploid

Question 10

Prophase II

Answer 10

The first phase of meiosis II. Prophase II is identical to mitotic prophase, except that the number of chromosomes was reduced by half during meiosis I.

The events of prophase II are essentially the same as those of mitotic prophase except that prophase II cells are haploid.

Question 11

Anaphase II

Answer 11

during anaphase II sister chromatids separate and migrate to opposite poles.

Question 12

telophase II and cytokinesis

Answer 12

In telophase II, nuclei form at opposite poles of each dividing cell, and cytokinesis splits the cells apart. Meiosis has produced four haploid cells, each with one set of chromosomes.

Four haploid cells are present at the end of telophase II and cytokinesis.

Question 13

During _____ sister chromatids separate.

Answer 13

Anaphase II

Question 14

telophase I and cytokinesis

Answer 14

The chromosomes finish their journey during telophase I, and cytokinesis occurs, producing two haploid daughter cells. Note that each chromosome still consists of two sister chromatids. Meiosis isn’t over yet; remember that it consists of two consecutive divisions. During meiosis II, the sister chromatids will be separated.

At the end of telophase I and cytokinesis there are two haploid cells.

Question 15

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

Answer 15

Telophase I

Question 16

prophase I

Answer 16

Prophase I begins with condensation of the chromosomes. Homologous chromosomes, each made up of two sister chromatids, come together in pairs. This pairing is called synapsis. Each chromosome pair is called a tetrad, a complex of four chromatids. Chromatids of homologous chromosomes cross over each other and exchange parts at chiasmata (singular, chiasma). Meanwhile, other cellular components prepare for the division of the nucleus. The centrosomes move away from each other, and spindle microtubules form between them. The nuclear envelope and nucleoli disperse. Finally, spindle microtubules capture the kinetochores that form on the chromosomes, and the chromosomes begin moving to the metaphase plate.

Homologous chromosomes pair

Question 17

metaphase II

Answer 17

During metaphase II, the chromosomes align on the metaphase plate.

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

Question 18

metaphase I

Answer 18

At metaphase I, the chromosome tetrads are aligned on the metaphase plate. For each tetrad, kinetochore microtubules from one pole of the cell are attached to one homologous chromosome, while kinetochore microtubules from the other pole of the cell are attached to the other chromosome of the pair. Thus, the homologous chromosomes are poised to move to opposite poles of the cell.

During metaphase I tetrads align along the metaphase plate.

Question 19

Synapsis occurs during _____.

Answer 19

Prophase I

Question 20

Homologous chromosomes migrate to opposite poles during _____.

Answer 20

Anaphase I

Question 21

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

Answer 21

Metaphase II

Question 22

anaphase I

Answer 22

During anaphase I, each pair of chromosomes is pulled apart and the homologous chromosomes move toward opposite poles. Note that sister chromatids remain attached at their centromeres and move as a unit toward the same pole.

During anaphase I homologous chromosomes, consisting of sister chromatids, migrate to opposite poles.

Question 23

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

Answer 23

telophase II, telophase II

Question 24

During _____ a spindle forms in a haploid cell.

Answer 24

Prophase II

Question 25

interphase

Answer 25

Like mitosis, meiosis is preceded by an interphase, during which the chromosomes replicate. The centrosome also duplicates in preparation for cell division. During interphase the centrosome duplicates and the chromosomes are not condensed.

Question 26

A cell at the end of S phase (DNA synthesis phase of interphase) contains 100 picograms of nuclear DNA. If this cell undergoes meiosis, how much nuclear DNA will be in each daughter cell?

Answer 26

25 picograms

Question 27

A cell at the end of S phase (DNA synthesis phase of interphase) contains 100 picograms of nuclear DNA. If this cell undergoes meiosis, there will be 25 picograms of nuclear DNA in each daughter cell.

Answer 27

G1 comes before S phase, when DNA is replicated. As the cell goes into G2, it has 100 pg of DNA, so it had to have 50 pg of DNA in G1. Each of the two daughter cells will have 50 pg of DNA at the end of meiosis I, and each of the four daughter cells will have 25 pg of DNA at the end of meiosis II.

Question 28

A normal diploid cell in G1 has 2 pg of DNA. At the end of meiosis I, one daughter cell __________.

Answer 28

is haploid and has 2 pg of DNA

Question 29

A normal diploid cell in G1 has 2 pg of DNA. At the end of meiosis I, one daughter cell is haploid and has 2 pg of DNA.

Answer 29

During meiosis I, the diploid (2n) parent cell produces two haploid (n) daughter cells. Notice, however, that each chromosome still consists of two sister chromatids, meaning that chromosomes are still replicated at the end of meiosis I. Remember that G1 comes before S phase, when DNA is replicated. As the cell goes into G2, it has 4 pg of DNA.

Question 30

The cells that produce sperm in humans contain 46 chromosomes. If one of these cells undergoes meiosis to form sperm cells, and chromosomal nondisjunction occurs in chromosome 22 during meiosis I, what is the chromosome number in each of the resulting sperm?

Answer 30

24, 24, 22, and 22 because n = 23

Question 31

When during meiosis do homologous chromosomes pair up?

Answer 31

Prophase 1