Chapter 11

Question 1

what is meiosis?

Answer 1

the division of a diploid parent cell into 2 haploid daughters

Question 2

what is a diploid in meiosis?

Answer 2

homologous pairs

Question 3

what is a haploid in meiosis?

Answer 3

half of a homologous pair

Question 4

what are gametes?

Answer 4

sex cells

Question 5

why is meiosis important?

Answer 5

it produces genetic variation, which is essential for a population to survive

Question 6

what is alternation of generations?

Answer 6

some organisms, like fungi and some plants, spend most of their lives as haploid, and only become diploid for a short period of time before returning to haploid form

Question 7

what is synapsis and when does it take place?

Answer 7

in meiosis I, members of homologous pairs (maternal and paternal) come in close physical contact with each other to exchange genetic information

Question 8

how many rounds of division does meiosis include?

Answer 8

2; meiosis 1 and meiosis 2

Question 9

what is the synaptonemal complex?

Answer 9

the structure formed when members of a homologous pair come into contact with each other during synapsis

Question 10

what is crossing over?

Answer 10

the exchange of genetic material between homologous pair (nonsister chromatids), is totally random, could happen, could not

Question 11

what is a chiasmata?

Answer 11

the location of the crossing over event

Question 12

what does crossing over do from an evolutionary standpoint?

Answer 12

increases variation

Question 13

between which nonsister chromatids does crossing over occur?

Answer 13

recombinant chromatids

Question 14

what does meiosis do in terms of chromosome number?

Answer 14

reduces chromosome number from diploid to haploid

Question 15

what does meiosis I separate?

Answer 15

homologous pairs

Question 16

what does meiosis II separate?

Answer 16

sister chromatids

Question 17

what does meiosis II yield?

Answer 17

4 cells with 2 replicated chromosomes

Question 18

what 4 things happen in prophase I of meiosis?

Answer 18

1. chromosomes begin to condense
2. spindle begins to form
3. nuclear membrane breaks down
4. synapsis occurs?

Question 19

what happens in metaphase I of meiosis?

Answer 19

pairs of homologous chromosome line up along the metaphase plate (ATTACHED BY KINETOCHORES), with each member of the homologous pair on opposite sides of the metaphase plate

Question 20

how does metaphase I of meiosis lead to genetic variation?

Answer 20

there are lots of alignment possibilities for the chromosomes

Question 21

what happens in anaphase I of meiosis?

Answer 21

kinetochore microtubules shorten, pulling apart HOMOLOGOUS PAIRS, maternal and paternal, NOT sister chromatids

Question 22

what happens in telophase I?

Answer 22

separated homologues form a cluster at each pole of the cell, nuclear envelope reforms around each daughter cell nucleus

Question 23

are sister chromatids identical in telophase I? why or why not?

Answer 23

no, crossing over has occurred

Question 24

what does meiosis II resemble?

Answer 24

a mitotic division

Question 25

what does prophase II follow?

Answer 25

a brief interphase with no S phase

Question 26

what happens in prophase II?

Answer 26

spindle apparatus forms in each daughter cell from meiosis I, nuclear envelope breaks down

Question 27

does the nuclear envelope always reform in telophase I?

Answer 27

no, in some species, it doesn’t reform in telophase I, removing the need for a 2nd breakdown in prophase II

Question 28

what happens in metaphase II?

Answer 28

there is a completed spindle apparatus in each cell, SISTER CHROMATIDS line up on opposite sides of metaphase plate

Question 29

what happens in anaphase II?

Answer 29

microtubules shorten, pulling apart SISTER CHROMATIDS to opposite poles of the cells

Question 30

what happens in telophase II?

Answer 30

nuclear membranes reform around 4 different clusters of chromosomes

Question 31

what results from telophase II after cytokinesis?

Answer 31

4 haploid cells

Question 32

are the haploid cells formed after meiosis II identical? why or why not? (2 reasons)

Answer 32

not identical, due to random alignment of homologous pairs in metaphase I and crossing over in prophase I

Question 33

list the number of chromosomes at each major stage of meiosis, assuming that the original haploid number is 3 chromosomes

Answer 33

1. 3 chromosomes in each maternal and paternal cell
2. 6 chromosomes in diploid offspring after meiosis I
3. 3 chromosomes in each potential gamete after meiosis II

Question 34

list the 5 differences between mitosis and meiosis

Answer 34

1. crossing over only occurs in meiosis, not mitosis
2. mitosis produces 2 diploid cells, meiosis produces 4 haploid cells
3. mitosis occurs in somatic cells, meiosis occurs in germ (sex) cells only
4. the daughter cells of mitosis are genetically identical to the parent cell, but the daughter cells from meiosis feature genetic variation from the parent cells
5. there is only one division cycle in mitosis, where meiosis has 2 division cycles

Question 35

list 3 similarities between mitosis and meiosis

Answer 35

1. both start with a diploid parent cell
2. in mitosis metaphase, and meiosis metaphase II, sister chromatids align on opposite sides of the metaphase plate
3. both utilize cytokinesis, once for mitosis, and twice for meiosis

Question 36

list the differences between metaphase I and anaphase I in meiosis and metaphase and anaphase in mitosis

Answer 36

metaphase I and anaphase I line up and pull apart members of homologous pairs, while metaphase and anaphase in mitosis line up and pull apart sister chromatids