- process of gamete formation

- morphological changes in germ cell 

(gametes)

- you get 1/2 the number of chromosomes

- haploid number is (2N)

- each germ cell only receives one copy of a chromosome

- All germ cells undergo 1st duplication of DNA in chromosomes

- A reduction division

- separation of homologous chromosomes

- 4N --> 2N

- the equitational division

- separation of chromatin in each chromosome

- 2N --> 1N

- you have 4 cells with 23 chromosomes

1. Leptotene

2. Zygotene

3. Pachytene

4. Diplotene

5. Diakinesis

- The condensation of chromatin

- Sister chromatics become connected

- Specific cohesion complexes (rec8p)

- Pairing of chromosome is initiated

- synapsis of homozyous chromosomes

- formation of synaptonemal complex

- forms a tetrad

-crossing-over of different chromatids

- Condensation still occuring

- Homologous chromosomes start to separate from each (disjunction)

- Chiasmata appears

- Condensation of chromosomes

- Nucleolus disappears and nuclear membrane disintegrates 

- Provide constancy of chromosome #

- Allows independent assortment

- Allows for crossing over of gene

- Distrubance occurs in non-disjunctions

Autosomal*****

Down syndrome: trisomy 21

Turner Syndrome: monosomy (reduced height/infertility)

Sex-linked****

Kliefelter's syndrome: increased height/ sterility