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MEIOSIS
HOW SEX CELLS ARE
MADE!
Make gametes by.....
MEIOSIS!!!!!!!!!
Meiosis forms haploid cells.
INTERPHASE OCCURS ONCE
G and S phases help enlarge the cell
and replicate the genetic material
Prepares the cell for nuclear division
1. PROPHASE I
Chromosomes
become visible.
Nuclear
Envelope
disappears
Crossing over
can occur.
2. METAPHASE I
Chromosome
s line up in
the middle
3. ANAPHASE I
homologous
pairs move to
opposite
poles
4. TELOPHASE I
Cytokinesis
5. PROPHASE II
no
interphase!
New spindles
form
6. METAPHASE II
Chromosome
s line up
again
7. ANAPHASE II
Centromeres
divide
Chromatids
move apart
8. TELOPHASE II
CYTOKINESI
S
RESULTS............
4 Haploid cells!
meiosis contributes to
genetic variation.
Gamete formation in male & female
animals involves meiosis.
Sperm are formed by
spermatogenesis
4 sperm are made by
meiosis
Ova (eggs) are made by oogenesis.
Only 1 egg results.
The other 3 are called polar-bodies.
The polar bodies die
SEXUAL VS. ASEXUAL
REPRODUCTION
SEXUAL REPRODUCTION...
2 parents form haploid
gametes.
The offspring will have traits of
both parents.
Advantage: mixes genes
Disadvantage: numbers are
limited
ASEXUAL REPRODUCTION
produces offspring that are
clones of parents
advantage: makes many
babies in short time
disadvantage: no diversity in
unstable environments
Examples of asexual reproduction:
binary fission: bacteria
budding: sponges
fragmentation: sea stars