Week 5_Meiosis in more detail

Question 1

what are the phases of meiosis?

Answer 1

interphase (G1, S, G2)

1 diploid cell –> 2 chromatids/chromosome

meiosis I (reduction division):
- prophase I
- metaphase I
- anaphase I
- telophase I

2 haploid cells –> 2 chromatids/chromosome
- homologous chromosomes are segregated

interkinesis (a rest period)

meiosis II:
- prophase II
- metaphase II
- anaphase II
- telophase II

sister chromatids are segregated

4 haploid cells –> 1 chromatid/chromosome

Question 2

what occurs in prophase I?

Answer 2

(1) chromosomes condense

(2) nuclear membrane breaks down

(3) spindle poles begin to form

(4) homologous chromosomes pair up and form a complex called a bivalent or tetrad

Question 3

homologous chromosomes are held together in bivalents/tetrads by ___

Answer 3

synaptonemal complex proteins

Question 4

what is crossing over?

Answer 4

in a bivalent, genetic material can be exchanged b/n paired chromosomes

Question 5

crossing over ___ chromosomes and increases ___

Answer 5

rearranges chromosomes

increases genetic variation

Question 6

crossing over may occur ___ times along chromosomes

Answer 6

multiple

Question 7

crossing over only occurs during ___ when ___ are paired

Answer 7

prophase I

when homologs are paired

Question 8

what occurs during metaphase I?

Answer 8

(1) homologous pairs line up at the metaphase plate

(2) alignment of homologs on either side of the metaphase plate is random

Question 9

what does independent assortment ensure in metaphase I?

Answer 9

ensures each new cell contains a mixture of homologs from the mother and father leading to greater genetic diversity

Question 10

what occurs during anaphase I?

Answer 10

(1) synaptonemal complex proteins dissolve

(2) homologs separate

(3) homolog segregated to opposite spindle poles by kinetochore microtubules

Question 11

what occurs during telophase I?

Answer 11

(1) chromosomes begin to decondense

(2) spindle network breaks down

(3) nuclear membranes re-form

(4) cytokinesis divides the cell

(5) meiosis I is completed

(6) interkinesis

Question 12

what is interkinesis?

Answer 12

a period of rest in preparation for Meiosis II

Question 13

Meiosis I (features/reviews):

Answer 13

cell goes thru PMAT I

Question 14

homologs pair up to form ___ during ___

Answer 14

bivalents/tetrads

prophase I

Question 15

bivalents are held together by ___

Answer 15

synaptonemal complex proteins

Question 16

during crossing over, an exchange of DNA occurs between ___

Answer 16

homologs

Question 17

during crossing over, ___ occurs between homologs

Answer 17

an exchange of DNA

Question 18

in metaphase I, homologous pairs ___ (___)

Answer 18

align

independent assortment

Question 19

in anaphase I, homologs ___

Answer 19

separate and are segregated

Question 20

the result of meiosis I is…

Answer 20

2 haploid cells

2 chromatids/chromosome

Question 21

at the beginning of meiosis II, there are…

Answer 21

2 haploid cells

2 chromatids/chromosome

Question 22

is there any DNA replication in meiosis II?

Answer 22

no

Question 23

during meiosis II, cell goes thru ___

Answer 23

PMAT II

Question 24

during anaphase II…

Answer 24

sister chromatids segregate

Question 25

what is the result of meiosis II?

Answer 25

4 haploid cels

1 chromatid/chromosome

Question 26

cell prior to S-phase:

• haploid or diploid?
• 2 chromatid or 1 chromatid chromosomes?

Answer 26

diploid

1 chromatid chromosomes

Question 27

after S phase but prior to Meiosis I:

• haploid or diploid?
• 2 chromatid or 1 chromatid chromosomes?

Answer 27

diploid

2 chromatid chromosomes

Question 28

after Meiosis I prior to Meiosis II:

• haploid or diploid?
• 2 chromatid or 1 chromatid chromosomes?

Answer 28

haploid

2 chromatid chromosomes

Question 29

after Meiosis II:

• haploid or diploid?
• 2 chromatid or 1 chromatid chromosomes?

Answer 29

haploid

1 chromatid chromosomes