meiosis

Question 1

What is meiosis

Answer 1

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell

Occurs on the production of gametes – sperm, eggs 

Question 2

how many divisions does meiosis have?

Answer 2

2

Question 3

what is the general first meiosis division?

Answer 3

it is a reduction division in which homologous chromosomes are separated

Question 4

what are the steps of the first meiosis division

Answer 4

PROPHASE 1:
- chromosomes replicate to form sister chromatids

• nuclear membrane dissolves
• chromosomes condense
• spindle fibres appear
• to increase genetic diversity, homologous chromosomes cross over via chiasmata

PROMETAPHASE 1:
- spindle fibres attach to chromosomes

• chromosomes continue to condense

METAPHASE 1:
- homologous chromosomes align along the equator of the cell

• independent assortment occurs

this determines which gamete chromosomes are allocated

• leads to genetic diversity in offspring

ANAPHASE 1:
- spindle fibre retracts

• homologous chromosomes pulled to opposite poles of the cell

TELOPHASE & CYTOKINESIS 1:
telophase:
- the nuclear membrane reforms
- spindle fibres disappear

cytokinesis:
- cytoplasm and cell divide
- resulting in two cells that are haploid

Question 5

why are the steps of the second meiosis division

Answer 5

Prophase II and Prometaphase II

These stages are identical to their counterparts in meiosis

Metaphase II
- chromosomes line up in single file along the equator of the cell
- not in homologous pairs

Anaphase II
- sister chromatids are pulled to opposite poles of the equator

Telophase II

This stage is the same as telophase I.

Cytokinesis II
- cytoplasm and cell divide producing 2 non-identical haploid daughter cells.

• the net product is 4 non-identical haploid daughter cells
• These are fully formed gametes.