Pre-AP Biology: Meiosis

Covers Meiosis I and II

diploid

2 copies of each chromosome. aka 2n

haploid

1 copy of a chromosome. aka 1n/n.

gamete

a haploid sex cell

meiosis product

4 genetically unique gametes

meiosis i and ii

two phases that allow for a 2nd division so you get a haploid cell.

interphase

only occurs before meiosis i

meiosis i

filler card! drink some water :)

prophase i

• spindle fibers form

• longest and most complex phase

• synapsis occurs

• crossing over occurs

synapsis

homologous chromosomes form a tetrad: 2 chromosomes or 4 chromatids

crossing over

when a part of a chromosome is exchanged for part of another to produce unique combos

metaphase i

• tetrads align in the middle

• individual assortment occurs

individual assortment

random orientation of homologous pair to poles. doesn’t affect next orientation.

anaphase i

• pairs separate and move towards poles

• sis chromatids remain attached at centromeres

telophase i

• pole has haploid set of chromosomes

• cell splits (cytokinesis)

meiosis ii

• no interphase ii

• basically mitosis

nondisjunction

• can happen during i OR ii

• failure of one+ pairs of homologous chromosomes / sister chromatids to separate normally

• usually causes abnormal # of chromosomes in daughter cell