Ch 13:Meiosis and Sexual Life Cycles

Question 1

What are the two cell divisions in meiosis?

Answer 1

meiosis I and meiosis II

Question 2

How many daughter cells result from meiosis?

Answer 2

four daughter cells

Question 3

What are the four divisions in meiosis I?

Answer 3

prophase I, metaphase I, anaphase I, telophase I and cytokinesis

Question 4

What occurs in prophase I?

Answer 4

each chromosome pairs with its homolog and crossing over occurs

Question 5

What happens to the chromatids during the crossing over?

Answer 5

the DNA molecules of non-sister chromatids are broken (by proteins) and are rejoined to each other

Question 6

What are chiasmata?

Answer 6

x-shaped regions at the sites of crossovers

Question 7

What occurs in metaphase I?

Answer 7

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 pair

Question 8

What occurs in anaphase I?

Answer 8

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 9

What occurs during telophase I and cytokinesis?

Answer 9

in the beginning, each half of the cell has a haploid set of duplicated chromosomes, each chromosome still consists of two sister chromatids, cytokinesis usually occur simultaneously, forming two haploid daughter cells

Question 10

What are the four phases of meiosis II?

Answer 10

prophase II, metaphase II, anaphase II, telophase II and cytokinesis

Question 11

What occurs in prophase II?

Answer 11

a spindle apparatus forms and chromosomes (each still composed of two chromatids) move toward the metaphase plate

Question 12

What occurs in metaphase II?

Answer 12

the sister chromatids are arranged at the metaphase plate, the two sister chromatids of each chromosome are no longer genetically identical. the kinetochores of sister chromatids attach to microtubules extending from opposite poles

Question 13

What occurs in anaphase II?

Answer 13

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

Question 14

What occurs in telophase II and cytokinesis?

Answer 14

the chromosomes arrive at opposite poles, nuclei form, and the chromosomes begin decondensing

Question 15

What is the synaptonemal complex in prophase I?

Answer 15

a zipper-like structure that holds the homologs together tightly during the crossing over

Question 16

What occurs during synapsis in prophase I?

Answer 16

DNA breaks are repaired, joining DNA from one non-sister chromatid to the corresponding segment of another

Question 17

What are the three differences of meiosis compared to mitosis?

Answer 17

synapsis and crossing over in prophase I, alignment of homologous pairs at the metaphase plate, and separation of homologs during anaphase I