Meiosis

Diploid to Haploid

Crossing Over

• Synapsis- Homologous Pairs line up = Tetrad• During synapsis the chromstids within a homologous

pair may twist around each other and break off and attach to the other homologous pair = Crossing Over

• Results in exchange of genetic material between maternal and paternal chromosomes = genetic recombination

Law of Independent Assortment

• During metaphase, as the homologous pairs line up the orientation of maternal and paternal chromosomes is random– Not all maternal go to one side, and paternal the

other….it is mixed

• Law of independent assortment• As the homologous pairs are separated in

anaphase, they maternal and paternal chromosomes have random separation– Results in genetic variation

Law of Independent Assortment

Formation of Gametes

• Meiosis only occurs in the reproductive cells…all other cells undergo mitosis

• Ending products of meiosis are haploid gametes– Eggs in female - oogenesis– Sperm in male - spermatogenesis

• Fusion of sperm and egg results in a diploid cell

DNA v. Gene

Karyotype

• 46 chromosomes, 23 pair• One of each pair was from mom, one from dad