1. AP Biology
Meiosis Part 2

2. Mom and Dad’s DNA contribution The egg surrounded by sperm.

3. TWO Divisions

4. Interphase

5. (First Division)

6. (Second Division)

7. Spermatogenesis Epididymis Seminiferous tubule Testis Cross section
of seminiferous
tubule
Spermatogonium
Mitotic division, producing
large numbers of spermatogonia
Sertoli cell
nucleus
Differentiation and onset of meiosis I
Primary spermatocyte
(in prophase of meiosis I)
Meiosis I completed
Secondary spermatocyte
Meiosis II
Lumen of
Seminiferous tubule
Early
spermatids
Spermatids
(at two stages of
differentiation)
Differentiation
Sperm cells
Neck
Head
Midpiece
Tail
Plasma membrane
Acrosome
Nucleus
Mitochondria

8. Oogenesis in the ovaries
Ovary
Primary germ cell
in embryo
Differentiation
Oogonium
in ovary
Oogonium
Mitotic
division
Primary
oocyte
within
follicle
Primary
oocyte
Completion of meiosis I
and onset of meiosis II
Growing
follicle
Secondary
oocyte
First polar body
Ovulation
Entry of sperm
triggers
completion
of meiosis II
Mature follicle
Ruptured
follicle
Second polar body
Ovum
Ovulated
secondary oocyte
Corpus luteum
Degen-
erating corpus luteum

9. Crossover in Prophase I

10. Mitosis vs. Meiosis

11. (before chromosome replication)
MITOSIS
MEIOSIS
Parent cell
(before chromosome replication)
Chiasma (site of
crossing over)
MEIOSIS I
Propase
Prophase I
Chromosome
replication
Chromosome
replication
Tetrad formed by
synapsis of homologous
chromosomes
Duplicated chromosome
(two sister chromatids)
2n = 6
Chromosomes
positioned at the
metaphase plate
Tetrads
positioned at the
metaphase plate
Metaphase
Metaphase I
Anaphase
Sister chromatids
separate during
anaphase
Homologues
separate
during
anaphase I;
sister
chromatids
remain together
Anaphase I
Telophase
Telophase I
Haploid
n = 3
Daughter
cells of
meiosis I 2n 2n
MEIOSIS II
Daughter cells
of mitosis n n n n
Daughter cells of meiosis II
Sister chromatids separate during anaphase II

12. Independent Assortment
Key
Maternal set of
chromosomes
Possibility 1
Possibility 2
Paternal set of
chromosomes
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Daughter
cells
Combination 1
Combination 2
Combination 3
Combination 4