Meiosis

Question 1

Meiosis:

Answer 1

• leads to independant assortment of chromosomes and unique composition of alleles in daughter cells
• is a reduction division of the nucleus to form haploid gametes
• process of a single cell dividing twice to produce four cells containing half its original genetic information (1 –> 2 –> 4)

Question 2

Process of Meiosis:

Answer 2

Interphase
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1

Prophase 2
Metaphase 2
Anaphase 2
Telophase 2

IPMAT PMAT

Question 3

Interphase:

Answer 3

1. DNA replication occurs

2. chromosomes are replicated and the copies are attached at the centromere

Question 4

Prophase 1:

Answer 4

1. homologous chromosomes associate with each other to form bivalents (synapsis)
2. crossing over between non-sister chromatids can occur, resulting in a recombination of alleles

Question 5

Metaphase 1:

Answer 5

1. random orientation occurs and each bivalent aligns independantly (this gives the daughter nuclei a mix of chromosomes)
   - this step is a significant source of genetic variation

Question 6

Anaphase 1:

Answer 6

1. homologous pairs are separated but the sister chromatids remain attached (called reduction division)

Question 7

Telophase 1:

Answer 7

1. set of chromosomes is seen at each pole
2. spindle breaks down and the cell separates across it’s middle with nuclear envelopes forming around the two new nuclei
3. cytokinesis completes the first stage of meiosis
   - brief interphase occurs but no DNA is duplicated

Question 8

Prophase 2:

Answer 8

1. the cell enters the second meiotic division

2. the spindle fibres reform and the nuclear envelope breaks down

Question 9

Metaphase 2:

Answer 9

1. pairs of sister chromatids align at the equator
2. spindle fibres attach at the centromere
3. random orientation again contributes to variation in the gametes (due to difference between chromatids where crossing over took place)

Question 10

Anaphase 2:

Answer 10

1. spindle fibres contract, splitting the centromeres

2. the sister chromatids are separated and the chromatids (now chromosomes) are pulled to opposing poles

Question 11

Telophase 2:

Answer 11

1. new haploid nuclei are formed
2. cytokinesis begins splitting the cells
3. final result is four haploid gamete cells