ch. 11 meiosis and sexual reproduction

Question 1

what does meiosis produce?

Answer 1

haploid gametes that contain half of the chromosomes of diploid somatic cells

Question 2

how many gametes will one diploid germ produce through meiosis?

Answer 2

4

Question 3

what is a zygote?

Answer 3

the 2N/diploid created from fertilization

Question 4

what happens during prophase 1?

Answer 4

-replicated chromosomes coil tighter
-nuclear envelope dissolves
-homologues undergo synapsis
-crossing over occurs between non-sister chromatids

Question 5

what is synapsis?

Answer 5

when the homologous chromosomes line up across from each other following replication

Question 6

what is the synaptonemal complex?

Answer 6

where proteins between the homologues are held

Question 7

what is crossing over?

Answer 7

genetic recombination between non-sister chromatids (physical exchange of regions between the homologues)

Question 8

what is the chiasmata?

Answer 8

the sites of crossing over

Question 9

what happens during metaphase I?

Answer 9

-terminal chiasmata hold homologues together after crossing over
-microtubules from opposite poles attach to each homologue
-homologues align at the metaphase plate across from one another
-the distribution of each pair of homologues on the metaphase I plate is random (random or independent assortment)
-pairs of homologues randomly assort and align opposite one another along the metaphasic plate
-microtubules from each pole attach to the kinetochores of homologues in their half of the cell

Question 10

what happens during anaphase I?

Answer 10

-microtubules of the spindle shorten
-homologues are separated from each other
-sister chromatids remain attached to one another at their centromeres

Question 11

what happens during telophase I?

Answer 11

-nuclear envelopes form around each set of chromosomes
-each new nucleus is now haploid
-sister chromatids are no longer identical because of crossing over

Question 12

what happens during prophase II?

Answer 12

nuclear envelopes dissolve and spindle apparatus forms

Question 13

what happens during metaphase II?

Answer 13

sister chromatids align on metaphase plate (cohesin on the metaphasic plate)

Question 14

what happens during anaphase II?

Answer 14

sister chromatids separate

Question 15

what happens during telophase II?

Answer 15

nuclear envelope reforms; cytokinesis follows

Question 16

what happens After crossing over in the early stages of meiosis I?

Answer 16

the homologues separate from one another in anaphase I

Question 17

Meiosis is distinguished from mitosis by:

Answer 17

1. Synapsis and crossing over in meiosis I
2. Sister chromatids remain joined at their centromeres in meiosis I
3. Kinetochores of sister chromatids attach to the same pole in meiosis I
4. DNA replicates once, but cell divides twice

Question 18

what do genetic differences arise from?

Answer 18

1) crossing over in meiosis I
2) random or independent assortment of homologues in metaphase I

Question 19

how many chromosomes do mosquitoes have?

Answer 19

6

Question 20

how many chromosomes do fruit flies have?

Answer 20

8

Question 21

how many chromosomes does garlic have?

Answer 21

16

Question 22

how many chromosomes does a mouse have?

Answer 22

40

Question 23

how many chromosomes does a red vischacha rat have?

Answer 23

102

Question 24

how many chromosomes does an atlas blue butterfly have?

Answer 24

448

Question 25

what is unique about meiosis in plants?

Answer 25

have an alternation of multicellular generations with both multicellular diploid (2N) and multicellular haploid (1N) stages. This is a haplodiplontic life cycle