Meiosis

Question 1

What are the two sex cells that fuse to form a fertilised egg known as?

Answer 1

Gametes

Question 2

What happens in meiosis I?

Answer 2

Reduction division.
The pairs of homologous chromosomes are separated into two cells.
Goes from one diploid cell to two haploid cells

Question 3

What happens in meiosis II?

Answer 3

The pairs of chromatids (chromosomes) present in each daughter cell are separated into two more cells.

Question 4

What is the final product of meiosis II?

Answer 4

Four haploid daughter cells

Question 5

What happens during prophase I?

Answer 5

• Chromosomes condense
• Nuclear envelope disintegrates
• The nucleolus disappears
• Spindle formation begins
• Crossing over

Question 6

What is crossing over?

Answer 6

In prophase I, homologous chromosomes pair up to form bivalents. They then trade exchange genes, forming recombinant chromosomes

Question 7

What happens in metaphase I?

Answer 7

Homologous chromosomes line up in pairs along the metaphase plate; this results in independent assortment

Question 8

When does independent assortment occur?

Answer 8

In both metaphase I and II

Question 9

What is independent assortment?

Answer 9

Where the orientation of each homologous pair along the metaphase plate is random and independent of any other homologous pair.
There is also independent assortment of chromatids in metaphase II.

Question 10

What happens in anaphase I?

Answer 10

Homologous chromosomes are separated, and are pulled to opposite polls of the cell

Question 11

What happens in telophase I?

Answer 11

• Chromosomes assemble at either pole
• Chromosomes uncoil
• Nuclear envelope reforms around the chromosomes
• The nucleolus reappears

Question 12

What happens in prophase II?

Answer 12

• Chromosomes condense
• Nuclear envelope disintegrates
• The nucleolus disappears
• Spindle formation begins
• Crossing over does not occur

Question 13

What happens in metaphase II?

Answer 13

Individual chromosomes line up along the metaphase plate. Independent assortment occurs again, in which the orientation of chromatids is random (i.e. they could be facing either pole)

Question 14

Given that metaphase II and metaphase of mitosis are so similar, why doesn’t independent assortment occur in mitosis?

Answer 14

In meiosis II, the chromosomes present are recombinant chromosomes, meaning the chromatids are non-identical; in contrast, in mitosis crossing over does not occur so the chromatids are identical

Question 15

What happens in anaphase II?

Answer 15

Chromatids of individual chromosomes are pulled to opposite poles after the division of the centromeres

Question 16

What happens in telophase II?

Answer 16

• Chromatids assemble at either pole
• Chromatids uncoil
• Nuclear envelope reforms around the chromatids
• Nucleolus reappears