Pre – AP Biology

Process of Meiosis (5.4)

Somatic vs. Germ

Female XX Karyotype(Remember… “kary” means “nucleus”)

Male XY Karyotype

Germ cells

TWO Divisions of Meiosis

Meiosis I -First Division

Meiosis II - Second Division

Spermatogenesis

Spermatogonium

Primary spermatocyte(in prophase of meiosis I)

Mitotic division, producinglarge numbers of spermatogonia

Meiosis I completed

Differentiation and onset of meiosis I

Secondary spermatocyte

Meiosis II

Earlyspermatids

Spermatids(at two stages ofdifferentiation)

Differentiation

Sperm cells Neck

Head Midpiece TailPlasma membrane

MitochondriaAcrosome Nucleus

Sertoli cellnucleus

Lumen ofSeminiferous tubule

Oogenesis in the ovaries

Primary germ cellin embryo

Mitoticdivision

Primaryoocyte

Ovary

Oogonium

Differentiation

Secondaryoocyte

Completion of meiosis Iand onset of meiosis II

Ovulation

First polar body

Entry of spermtriggerscompletionof meiosis IISecond polar body

Ovum

Variation is the outcome desired

Mitosis vs. Meiosis