Cell division

Chromosomes

DNA which is wound around histone proteins

Interphase

Replicating DNA

Cell grows

Replicates organelles

Describe meiosis 1

Prophase - Homologous pairs form bivalents, crossing over happens

Metaphase - Bivalents line up on equator causing random assortment

Anaphase - chromosomes pulled apart by centromeres

Telophase - chromosomes reach poles

Describe meiosis 2

Prophase - chromosomes condense, spindle forms

Metaphase - Chromosomes line up on equator causing random assortment

Anaphase - chromatids pulled to poles

Telophase - Nuclear membrane now forms

What causes variation

Crossing over in prophases

Random assortment in metaphases

Why do we need to do mitosis (2)

Living things grow by producing more cells

Repair damaged tissues

4 stages of mitosis

Pro, meta, ana, telophase

What happens in prophase

Chromosomes coil up

Spindle fibres form

What happens in metaphase of mitosis

Chromosomes line up on middle

Spindle attatches to centromere

Anaphase of mitosis

Centromeres divide

Pull chromatids apart

Telophase of mitosis

Reach poles and unwind

What happens during cytokinesis in animal and plants cells

Cell cytoplasm pinches in

Cell plate forms

Homologous pair

Contains same genes as the other but may have a different allele