Meiosis

Question 1

What is meiosis?

Answer 1

Leads to the production of haploid gametes or spore
• produces genetically variable cells

Question 2

What happens in meiosis 1?

Answer 2

• separation of homologous chromosome pairs
• reduction of the chromosome number by half (reduction division)
• 2n —> n

Question 3

What happens in meiosis 2?

Answer 3

• separation of sister chromatids
• also known as equational division
n —> n

Question 4

What are the steps of meiosis I?

Answer 4

1. Prophase 1
2. Metaphase 1
3. Anaphase 1
4. Telophase 1

Question 5

What is process between meiosis I and II called?

Answer 5

Interkinesis

Question 6

What happens in interkinesis?

Answer 6

• nuclear membrane reforms around the chromosomes clustered at each pole
• spindle breaks down
• chromosomes relax

Question 7

What happens in prophase 1?

Answer 7

• chromosomes begin to condense and the spindle forms
• homologous chromosomes pair
• crossing over takes place
• the nuclear membrane breaks down

Question 8

What are the five stages of prophase 1?

Answer 8

1. Leptotene
2. Zygotene
3. Pachytene
4. Diplotene
5. Diakinesis

Question 9

What happens in leptotene?

Answer 9

Chromosomes condense and become visible

Question 10

What happens in zygotene?

Answer 10

• homologous chromosomes pair up and begin synapsis

Question 11

What is synapsis?

Answer 11

Close pairing of homologous chromosomes

Question 12

What is a tetrad?

Answer 12

• closely associated homologous chromosomes
• 4 copies of dna
Consists of 4 chromatids

Question 13

What happens during pachytene?

Answer 13

• chromosomes become shorter and thicker
• synaptonemal complex develops between homologous chromosomes

Question 14

What happens during diplotene?

Answer 14

• centromeres of paired chromos move apart
• the two homologs remain attached at chiasmata

Question 15

What is a the chiasmata?

Answer 15

• where the 2 chromos cross

Question 16

What happens during diakinesis?

Answer 16

• chromosomes condensation continues
• nuclear membrane breaks down
• spindle forms
• crossing over happens

Question 17

What happens in metaphase 1?

Answer 17

Random alignment of homologous pairs of chromosomes along the metaphase plate

Question 18

What happens in anaphase 1?

Answer 18

The homologous chromosomes separate and move toward opposite poles

Question 19

What happens in telophase 1?

Answer 19

Chromosomes arrive at the spindle poles and the cytoplasm divides

Question 20

What happens in prophase 2?

Answer 20

INTERKINESIS REVERSED
• Chromosomes recondense
• spindle reforms
• nuclear membrane breaks down

Question 21

What happens in metaphase 2?

Answer 21

• replicated chromos line up on metaphase plate
• sister chromatids facing opposite poles

Question 22

What happens in anaphase 2?

Answer 22

• sister chromatids separate
• chromatids are pulled to opposite poles
• each chromatid is now a distinct chromosome

Question 23

What happens in telophase 2?

Answer 23

• Chromos arrive at spindle poles
• the spindle breaks down
• nuclear membrane re-forms around the chromos
• cytoplasm divides
• Chromos relax

Question 24

What are the products of meiosis?

Answer 24

• 4 haploid cells
• n

Question 25

In what cell division process does crossing over happen?

Answer 25

ONLY in meiosis 1

Question 26

In what cell division process does crossing over happen?

Answer 26

ONLY in meiosis 1

Question 27

What is cohesin?

Answer 27

• ring like, protein complex structure that holds the chromatids together • key to the behavior of chromosomes in mitosis and meiosis

Question 28

What does the breakdown of cohesin allow?

Answer 28

It allows sister chromatids to separate

Question 29

What breaks down cohesin?

Answer 29

Separase

Question 30

What happens in cytokinesis in meiosis 1?

Answer 30

The cytoplasm divides to produce two cells, each having half the original number of chromosomes.