MEIOSIS
8-3
http://waynesword.palomar.edu/lmexer2a.htm
Making gametes…
ALL LIVING THINGS
Reproduce
_______________
REPRODUCTION
No recombination of
genetic material;
ONLY ONE parent
Seen in bacteria and
some animals
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm
CELL DIVISION in PROKARYOTES
Bacteria
reproduce
using
__________________
•DNA is copied
•Cell splits into two
new cells
http://www.tnau.ac.in/notesbscag/agm/UGMicro/AGM151_201/theory_files/image156.jpg
BINARY FISSION
• Makes ____ cells
genetically identical
• Used to for
___________
reproduction
in bacteria
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html
ADVANTAGES OF
ASEXUAL REPRODUCTION
Can make offspring
faster
Don’t need a partner
http://www.mrgrow.com/images/cutting.jpg
DISVANTAGES OF
ASEXUAL REPRODUCTION
ALL ALIKE
Species CAN’T change
and adapt
One disease can wipe
out whole population
http://www.mrgrow.com/images/cutting.jpg
ALL LIVING THINGS
Reproduce
____________
REPRODUCTION
Combines the
genetic material from
2 parents (sperm & egg)
Family image from: http://babyhearing.org/Parenet2Parent/index.asp
ADVANTAGES OF SEXUAL
REPRODUCTION
Allows for variation in
population
Individuals can be different
Allow species adapt to
changes in their
environment
http://naturalsciences.sdsu.edu/classes/lab8/spindex.html
http://www.angelbabygifts.com/
EGG
+
SPERM 
If egg and sperm had same number of
chromosomes as other body cells ….
baby would have too many chromosomes!
MEIOSIS is the way…
http://waynesword.palomar.edu/lmexer2a.htm
to make
HAPLOID
(1n) cells
for
sexual
reproduction
DIPLOID & HAPLOID
Some cells have 2 copies of each
chromosome = _______________
(one from mom; one from dad)
• All BODY cells are diploid
Image from: http://www.ncu.edu.tw/~ls/graph/faculty_pictures/whole_time/SLC/SLC_lab-1.jpg
DIPLOID & HAPLOID
Some cells have only one copy of each
chromosome = ____________________
All sperm and egg cells
are haploid
MITOSIS
• Makes 2 cells genetically
identical to parent cell &
to each other
• Makes 2n cells
• Makes body cells
• Used to grow organisms,
repair injuries, replace
worn out cells
http://waynesword.palomar.edu/lmexer2a.htm
MEIOSIS
• Makes ____ cells
genetically different from
parent cell & from each
other
• Makes _____ cells
• Makes ______________
• Used for ____________
http://waynesword.palomar.edu/lmexer2a.htm
WHAT MAKES MEIOSIS
DIFFERENT ?
1. SYNAPSIS & CROSSING OVER
(PROPHASE I)
2. INDEPENDENT ASSORTMENT
(ANAPHASE I)
3. Skip INTERPHASE II (NO S)
CELL DIVIDES TWICE, BUT…
ONLY COPIES DNA ONCE
WHAT MAKES MEIOSIS
DIFFERENT ?
1. Homologous chromosomes pair up
during PROPHASE I =
______________________
Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
WHAT MAKES MEIOSIS
DIFFERENT?
1. Exchange of DNA between homologous
pairs = ________________________
during PROPHASE I
Produces daughter cells
with different gene
combinations
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
HOMOLOGOUS PAIR
• Same size
• Same shape
• Carry genes for the
same traits, but ….
THEY ARE NOT
IDENTICAL
Can carry different
gene choices
Image modified from: http://arnica.csustan.edu/biol3020/cell_division/cell_division.htm
http://waynesword.palomar.edu/lmexer2a.htm
WHAT MAKES MEIOSIS
DIFFERENT ?
2. Mixing up of maternal and paternal
chromosomes during ANAPHASE I =
________________________________
INDEPENDENT ASSORTMENT
INDEPENDENT ASSORTMENT
at ANAPHASE I
Lots of different
combinations are
possible!
This is why you don’t
look exactly like your
brothers and sisters.
http://www.tokyo-med.ac.jp/genet/anm/mimov.gi
WHAT MAKES MEIOSIS
DIFFERENT ?
____________________________
and
__________________________________
Produce daughter cells that are
___________ from the parent cells
= ________________________________
WHAT MAKES MEIOSIS
DIFFERENT ?
1. Skip INTERPHASE II (No S)
CELL DIVIDES TWICE, BUT …
ONLY COPIES ITS DNA ONCE
MITOSIS:


1
G
S
G2  P  M  A

T C
MEIOSIS:
G1  S

G2  P M  A  T  C
P  M  A T  C
MITOSIS vs MEIOSIS
INTERPHASE INTERPHASE I
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
• DNA spread out as chromatin
• Nuclear membrane/
nucleolus visible
• DNA copied during S phase
• Make stuff new cell needs G2
Same as
MITOSIS
MITOSIS vs MEIOSIS
PROPHASE PROPHASE I
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
DNA scrunches into
chromosomes
Nuclear membrane/
nucleolus disappear
Centrioles/
spindle fibers appear
DNA scrunches into
chromosomes
Nuclear membrane/
nucleolus disappear
Centrioles/spindle fibers
appear
MITOSIS vs MEIOSIS
METAPHASE
METAPHASE I
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
• Chromosomes line up
in middle
Chromosomes line up
in middle
MITOSIS vs MEIOSIS
ANAPHASE ANAPHASE I
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
APART:
Chromatids split
APART:
Chromatids stay together
Homologous pairs split
MITOSIS vs MEIOSIS
TELOPHASE TELOPHASE I
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
See TWO nuclei
Nuclear membrane/
nucleolus return
DNA spreads out as
chromatin
SAME AS MITOSIS
MITOSIS vs MEIOSIS
CYTOKINESIS CYTOKINESIS I
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
Cytoplasm splits
into 2 cells
SAME AS
MITOSIS
MITOSIS vs MEIOSIS
INTERPHASE II
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
• DNA spread out as chromatin
• Nuclear membrane/
nucleolus visible
• DNA copied during S phase
MITOSIS vs MEIOSIS
PROPHASE PROPHASE II
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
• DNA scrunches into
chromosomes
• Nuclear membrane/
nucleolus disappear
• Centrioles/
spindle fibers appear
SAME AS MITOSIS
MITOSIS vs MEIOSIS
METAPHASE
METAPHASE II
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
• Chromosomes line up
in middle
SAME AS MITOSIS
MITOSIS vs MEIOSIS
ANAPHASE ANAPHASE II
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
Chromatids split and
move apart
SAME AS MITOSIS
MITOSIS vs MEIOSIS
TELOPHASE TELOPHASE II
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
Two nuclei
Nuclear membrane/
nucleolus returns
Centrioles/spindle fibers
disappear
DNA spreads out as
chromatin
SAME AS MITOSIS
MITOSIS vs MEIOSIS
CYTOKINESIS CYTOKINESIS II
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
Cytoplasm splits
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
SAME AS MITOSIS
Ways Meiosis is different?
• Homologous pairs match up (SYNAPSIS)
in PROPHASE I
•CROSSING OVER (Prophase I) and
•INDEPENDENT ASSORTMENT
(Anaphase I)
create genetic recombination
• Skipping INTERPHASE II(Dividing TWICE but copying DNA once)
produces 1n cells
WHAT CAN GO WRONG?
One pair of chromosomes
fails to separate
One daughter cell
gets one extra chromosome
One daughter cell
is missing one chromosome
http://www.tokyo-med.ac.jp/genet/anm/domov.gif
WHAT CAN GO WRONG?
http://members.tripod.com/~yenial/chromosome.html
MAKING
SPERM & EGGS
PRODUCTION OF MATURE SPERM
= __________________________
Mature & grow flagella
Sperm provides DNA
All the starting nutrients,
organelles, molecule building blocks,
etc. have to come from the egg.
PRODUCTION OF A MATURE EGG=
__________________________
Produces:
1 “good” egg
3 POLAR
BODIES
CYTOPLASM DIVIDES UNEVENLY
POLAR BODIES DEGENERATE (DIE)
“Self digest”
Using
________________
= __________________
“cell suicide”