2.6.5 The Stages of Meiosis

Question 1

What is meiosis

Answer 1

• Produces haploids from diploids
• Produces gametes in plants and animals for sexual reproduction
• 2 divisions

Question 2

Prophase 1

Answer 2

• DNA condenses
• Chromosomes arrange side in homologous (bivalent) pairs
• At chiasmata, crossing over of genes occurs between homologous pairs of chromosomes
• Ensures genetic variation
• Centrioles migrate to opposite poles
• Nuclear membrane breaks down

Question 3

Metaphase 1

Answer 3

• Homologous pairs of chromosomes line up along equator
• Spindle fibres attach to centromeres from centrosomes
• Independent assortment occurs (maternal and paternal chromosomes randomly align at equator causing more genetic variation)

Question 4

Anaphase 1

Answer 4

• Homologous pairs of chromosomes separated
• Spindle fibres shorten
• Centromeres do not divide

Question 5

Telophase 1

Answer 5

• Chromosomes arrive at opposite poles
• Spindle fibres break down
• Nuclear envelope forms around 2 groups of chromosomes
• New nuclei form

Question 6

Cytokenesis

Answer 6

• Division of cytoplasm
• In animals, cell surface membrane pinches to create a cleavage furrow
• In plants, vesicles merge forming new cell surface membrane
• 2 haploid cells produced

Question 7

What is the second meiosis cycle like?

Answer 7

• Same as mitosis
• 4 haploid daughter cells produced
• No interphase between Meiosis 1 and 2 because DNA is not replicated

Question 8

What happens in Meiosis II?

Answer 8

Identical to Mitosis
- Cytokinesis occurs, forming 4 haploid cells