MEIOSIS
Chapter 13
Slide show modified from Tracy Jackson and Kim Foglia
http://waynesword.palomar.edu/lmexer2a.htm
DO NOW
• What are three differences between mitosis
and meiosis?
• HOMEWORK: Watch Bozeman Sordaria
Cross Video; take notes
Remember from Chapter 1:
CHARACTERISTICS OF LIVING THINGS
REPRODUCE
ALL LIVING THINGS __________
ASEXUAL
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm
Family http://babyhearing.org/Parenet2Parent/index.asp
SEXUAL
ASEXUAL REPRODUCTION
Bacteria reproduce using
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookmito.html
BINARY FISSION
__________________________________
http://fig.cox.miami.edu/~cmallery/150/mitosis/c7.13.2.hydra.jpg
Budding & regeneration are used by plants
and animals to reproduce asexually
(mitosis)
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm
BINARY FISSION & MITOSIS
identical
Produces cells that are __________
copies of parent cell
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
SEXUAL REPRODUCTION
Family image from: http://babyhearing.org/Parenet2Parent/index.asp
Combines genetic material
from 2 parents (sperm & egg)
Offspring are genetically
different from parents
ADVANTAGES OF
SEXUAL REPRODUCTION
Allows for variation in population
Individuals can be different
Provides foundation for EVOLUTION
Allow species adapt to
changes in
their environment
http://naturalsciences.sdsu.edu/classes/lab8/spindex.html
Image by Riedell
EGG
Image by Riedell
+
http://www.angelbabygifts.com/
SPERM 
If egg and sperm had same number of
chromosomes as other body cells . . .
baby would have too many chromosomes!
http://www.acmecompany.com/stock_thumbnails/13217.forty-six_chromosomes.jpg
MEIOSIS is the way…
http://waynesword.palomar.edu/lmexer2a.htm
to make cells
with ½ the
number of
chromosomes
for sexual
reproduction
DIPLOID & HAPLOID
Most cells have 2 copies of each chromosome
DIPLOID
2n
= ______________
(one from mom; one from dad)
HOMOLOGOUS
CHROMOSOMES
All BODY (___________)
= SOMATIC
cells are diploid
Chromosomes that determine
the sex of an organism =
_________________
Sex chromosomes
http://www.angelbabygifts.com/
All other chromosomes =
_________________
autosomes
Humans have two sex chromosomes
X
y
and _____
44 autosomes
KARYOTYPE is a picture of
A __________
an organism’s chromosomes
DIPLOID & HAPLOID
Some cells have only one copy of each
HAPLOID
1n
chromosome = _____________
All sperm and egg cells
are haploid
MITOSIS
• Makes ___
2 cells genetically
identical
_________
to parent cell &
to each other
2n
• Makes ___ cells
• Makes __________
SOMATIC (body)
• Used by organisms to:
increase size of organism,
repair injuries,
replace worn out cells
http://waynesword.palomar.edu/lmexer2a.htm
MEIOSIS
4 cells
• Makes ____
genetically different from
parent cell & from each
other
1n cells
• Makes _____
• Makes ______________
Germ cells
OR Gametes (sperm & eggs)
• Used for ____________
sexual
reproduction
http://waynesword.palomar.edu/lmexer2a.htm
WHAT MAKES MEIOSIS
DIFFERENT ?
1. SYNAPSIS & CROSSING OVER
(PROPHASE I)
2. SEGREGATION &
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
SYNAPSIS
= ______________
This group of FOUR (4)
chromatids is called a
TETRAD
_________________
Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
WHAT MAKES MEIOSIS
DIFFERENT?
1. Exchange of DNA between
OVER
homologous pairs = CROSSING
_____________
during PROPHASE I
Allows shuffling
of genetic material
Places where crossing over
happens
CHIASMATA
= ____________________
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
HOMOLOGOUS CHROMOSOMES
Image modified by Riedell
• SAME SIZE
• SAME SHAPE
• CARRY GENES for the
SAME TRAITS
IDENTICAL
• BUT NOT
______________!
(Don’t have to have the
SAME CHOICES)
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
Image modified by Riedell
CROSSING
OVER
rearranging of DNA
• Allows for_________________
in different combinations
• After crossing over, chromatid arms
NOT IDENTICAL anymore
are________________
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
SEGREGATION
(Anaphase I)
SEGREGATION & CROSSING OVER
together make even more combinations
See an
animation
http://waynesword.palomar.edu/lmexer2a.htm
INDEPENDENT ASSORTMENT
http://fig.cox.miami.edu/~cmallery/150/mitosis/c13x9independent-assortment.jpg
INDEPENDENT ASSORTMENT
at ANAPHASE I
Lots of different
combinations are
possible!
This is why you
don’t look exactly
like your brothers
and sisters even
though you share
the same parents!
http://www.tokyo-med.ac.jp/genet/anm/mimov.gi
GENETIC RECOMBINATION
comes from:
• Crossing over
• Segregation
• Independent assortment
• Random fertilization
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
MITOSIS vs MEIOSIS
INTERPHASE INTERPHASE I
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
• DNA is spread out as chromatin
• Nuclear membrane/
nucleolus visible
• DNA is copied during S phase
• Makes stuff new cell needs in 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
Homologous pairs match up
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
with homologous partner
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/
SAME AS MITOSIS
nucleolus return
DNA spreads out as chromatin
Spindle/centrioles disappear
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 is spread out as chromatin
SKIP
• Nuclear membrane/
INTERPHASE II
nucleolus visible
• DNA is copied during S phase DNA NOT COPIED
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 & trade DNA
(SYNAPSIS & CROSSING OVER) in
PROPHASE I
•SEGREGATION
& INDEPENDENT ASSORTMENT
in Anaphase I
create genetic recombination
• Skipping INTERPHASE II(Dividing TWICE but copying DNA once)
produces 1n cells
MAKING
SPERM & EGGS
Gametogenesis =
process of forming gametes (n) from diploid
(2n) cells
Spermatogenesis =
process of forming sperm cells
by meiosis in animals,
by mitosis in plants in specialized organs
After division all 4 cells undergo differentiation to
become sperm cells
SPERMATOGENESIS
___________________=
MAKING MATURE SPERM
Mature & grow flagella
Sperm provides DNA
All the starting nutrients,
organelles, molecule building blocks,
etc. have to come from the egg.
http://www.moondragon.org/obgyn/pregnancy/twins.html
OOGENESIS
__________________
=
MAKING a MATURE EGG
Produces:
1 “good” egg
3 POLAR
BODIES
CYTOPLASM DIVIDES UNEVENLY
http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20102/Bio%20102%20lectures/Animal%20Reproduction/animal.htm
POLAR BODIES DEGENERATE (DIE)
“Self digest”
Using
LYSOSOMES
________________
= __________________
APOPTOSIS
“cell suicide” for good of organism
http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20102/Bio%20102%20lectures/Animal%20Reproduction/animal.htm
Oogenesis = process of forming an ovum (egg)
by meiosis in animals
by mitosis in the gametophyte in plants
in specialized gonads known as ovaries.
Unlike spermatogenesis, cytoplasm divides unevenly so
that all cytoplasm/organelles go to 1 large egg.
3 other cells = polar bodies; do not develop. Thus, all
the cytoplasm and organelles go into the egg.
Human males produce 200,000,000 sperm per day,
while the female produces one egg (usually) each
menstrual cycle.
Life Cycles
• A life cycle is the
generation-togeneration sequence of
stages in the
reproductive history of
an organism, from
conception to
production of its own
offspring.
ALTERNATION OF GENERATIONS
IN PLANTS AND SOME ALGAE:
SPOROPHYTE =
____________
multicellular diploid stage in which meiosis
SPORES
makes haploid cells called _________
Spores give rise to
a multicellular
HAPLOID organism
GAMETOPHYTE
= ________________
without fusing
with another cell
Image from Biology Campbell and Reece
IN FUNGI and SOME PROTISTS:
Gametes fuse to make a diploid zygote
Meiosis occurs in zygote without
growing into a diploid organism
Meiosis makes
haploid cells that
grow into haploid
organisms which use
MITOSIS to make
GAMETES!
Image from Biology Campbell and Reece
Meiosis Animations
Frame-by-frame animation
• http://www.csuchico.edu/~jbell/Biol207/animations
/meiosis.html
Continuous animation – no words
• http://www.people.virginia.edu/~rjh9u/meioanim.ht
ml
Continuous frame-by-frame
• http://www.trentu.ca/biology/101/14.html