Phase 1

Front 1

Chromosomes replicate
Each replicated chromosome contains 2 genetically identical sister chromatids connected at the centromere
Centrosome replicates, forming 2 centrosomes

Back 1

Takes up more than 90% of time
Chromosomes condense
Homologous chromosomes pair along their lengths
DNA molecules in nonsister chromatids break at corresponding places and then rejoin during crossing over
In synapsis, a protein structure forms between homologues holding them tightly together
Protein disassembles and each chromosome pair is seen as a group of 4 chromatids
Nuclear envelope begins to break down
The homologous pairs move toward the metaphase plate

Front 2

Pairs of homologous chromosomes are arranged on the metaphase plate
Both chromatids of a homologue are attached to kinetochore microtubules from one pole

Back 2

Chromosomes move toward the poles
Sister chromatids remain attached at the centromere and move toward the same pole
Homologous chromosomes move toward opposite poles

Front 3

Cytokinesis forms 2 haploid duaghter cells
In animal cells a cleavage furrow is formed
In some cells the nuclear envelope and nucleoli re-form
No chromosome replication occurs

Back 3

A spindle apparatus forms
Chromosomes composed of 2 chromatids move toward the metaphase II plate

Front 4

Chromosomes are positioned on the metaphase plate
The kinetochores of sister chromatids are attached to microtubules extending from opposite poles

Back 4

Centrosomes of each chromosome finally separate and the sister chromatids come apart
Sister chromatids move individually towards opposite poles