Chapter 13

Question 1

Prophase I

Answer 1

• in early prophase I each chromosome pairs with its homolog and crossing over occurs
• X-shaped regions called chiasmata are sites of crossover

Question 2

Metaphase I

Answer 2

• pairs of homologs line up at the metaphase plate, with one chromosome facing each pole
• microtubules from one pole are attached to the kinetochore of one chromosome of each tetrad
• microtubules from the other pole are attached to the kinetochore of the other chromosome

Question 3

Anaphase I

Answer 3

• pairs of homologous chromosomes separate
• one chromosome of each pair moves toward opposite poles, guided by the spindle apparatus
• sister chromatids remain attached at the centromere and move as one unit toward the pole

Question 4

Telophase I

Answer 4

• each half of the cell has a haploid set of chromosomes; each chromosome still consists of two sister chromatids

Question 5

Cytokinesis usually occurs simultaneously forming:

Answer 5

two haploid daughter cells

Question 6

Prophase II

Answer 6

• a spindle apparatus forms

- chromosomes (each still composed of two chromatids) move toward the metaphase plate

Question 7

Metaphase II

Answer 7

• the sister chromatids are arranges at the metaphase plate (b/c of crossing over in meiosis I, the two sister chromatids od each chromosome are no longer genetically identical)
• the kinetochores of sister chromatids attach to microtubules extending from opposite poles

Question 8

Anaphase II

Answer 8

• the sister chromatids separate

- the sister chromatids of each chromosome now move as two newly individual chromosomes toward opposite poles

Question 9

Telophase II and Cytokinesis

Answer 9

• the chromosomes arrive at opposite poles
• nuclei from, and the chromosomes begin decondensing
• cytokinesis separates the cytoplasm
• at the end of meiosis, there are four daughter cells, each with a haploid set of unreplicated chromosmes
• each daughter cell is genetically distinct from the others and from the parent cell

Question 10

Mitosis ______ the number of chromosome sets, producing cells that are genetically identical to the parent cell

Answer 10

conserves

Question 11

meiosis _______ the number of chromosomes sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell

Answer 11

reduces

Question 12

mitosis occurs

Answer 12

in both diploid and haploid cells

Question 13

meiosis occurs in:

Answer 13

only diploid cells

Question 14

DNA replication in mitosis and meiosis

Answer 14

mitosis: occurs during interphase before mitosis begins
meiosis: occurs during interphase, before meiosis I begins

Question 15

Number of divisions in mitosis and meiosis

Answer 15

mitosis: one
meiosis: 2

Question 16

synapsis of homologous chromosomes in mitosis and meiosis

Answer 16

mitosis: does not occur
meiosis: occurs during prophase I along with crossing over between nonsister chromatids, resulting chiasmata hold pairs together due to sister chromatid cohesion