Meiosis

What is meiosis?

process that produces haploid gamete cells from diploid cells.

What is the significance of meiosis?

• keeps chromosome number constant in each generation

• generates genetic variation in the gametes

How does variation occur in meiosis?

• crossing over during Prophase I

• independent assortment during metaphase I and II

What happens during Interphase I?

• DNA replication

• cell growth

• organelles replicate

• proteins/ enzymes synthesised

What happens during Prophase I?

• nuclear envelope breaks down

• spindle fibres form

• lines up with homologous pair

• Chromatids : Condense

• crossing over occurs ( chiasmata)

What happens during Metaphase I ?

• homologous chromosomes line up aloe the equator - attach to spindle fibre by their centromeres

• independent assortment occurs where chromosomes line up randomly

What happens during anaphase I ?

• homologous chromosomes separated

• pulled to opposite poles

• reduction in chromosome number occurs from diploid to haploid

What happens during Telephase I ?

• reach opposite poles of the cells

• nuclear envelope reforms around chromosomes

What happens during Prophase II ?

• chromosomes condense

• nuclear envelope disintegrates

• spindle fibres form

What happens during Metaphase II ?

• chromosomes attach to spindle fibres by their centromeres

What happens during anaphase II ?

sister chromatids are separated

What happens during Telephase II ?

• reach opposite poles of the cells

• nuclear envelope reforms around chromosomes

What happens when cytogenesis takes place?

4 genetically unique daughter cells produced