MEIOSIS
11-4
http://waynesword.palomar.edu/lmexer2a.htm
Making gametes…
Interest Grabber
Interest Graber
1. How many chromosomes would a sperm or an egg contain if
either one resulted from the process of mitosis?
46 chromosomes
2. If a sperm containing 46 chromosomes fused with an egg
containing 46 chromosomes, how many chromosomes would the
resulting fertilized egg contain? Do you think this would create
any problems in the developing embryo?
46 + 46 = 92; a developing embryo would not survive if it
contained 92 chromosomes.
3. In order to produce a fertilized egg with the appropriate
number of chromosomes (46), how many chromosomes should
each sperm and egg have?
Sperm and egg should each have 23 chromosomes.
Remember from Chapter 1:
CHARACTERISTICS OF LIVING THINGS
REPRODUCE
ALL LIVING THINGS __________
Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm
Family http://babyhearing.org/Parenet2Parent/index.asp
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
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)
so offspring are
DIFFERENT
genetically __________
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
Video 1
Meiosis Overview
Click the image to play the video segment 11A.
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 ______________
Gametes
(sperm & eggs)
• Used for ____________
sexual
reproduction
http://waynesword.palomar.edu/lmexer2a.htm
WHAT MAKES MEIOSIS
DIFFERENT?
1. Exchange of DNA between
OVER
homologous pairs = CROSSING
_____________
during PROPHASE I
Allows shuffling
of genetic material
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 & CROSSING OVER
together make even more combinations
See an
animation
http://waynesword.palomar.edu/lmexer2a.htm
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
MAKING
SPERM & EGGS
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.
OOGENESIS
__________________
=
MAKING a MATURE EGG
Produces:
1 “good” egg
3 POLAR
BODIES
CYTOPLASM DIVIDES UNEVENLY
WHY MAKE ONLY ONE “GOOD” EGG?
Sperm
donates
mostly DNA
Most of the cell parts and nutrients
needed for baby come from EGG!
http://bestweekever.blogs.com/photos/uncategorized/imagemain_sperm_egg1_1.gif