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MEIOSIS
11-4
http://waynesword.palomar.edu/lmexer2a.htm
Making gametes…
Interest Grabber
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
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)
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.
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
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
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
Video 5
Crossing Over
SEE CROSSING OVER
ANIMATION
Click the image to play the video segment. 11E
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
WHAT MAKES MEIOSIS
DIFFERENT ?
2.Separation
during ANAPHASE I
SEGREGATION &
INDEPENDENT ASSORTMENT
Separates gene choices and allows
shuffling of genetic material
Video 4
Segregation of Chromosomes
Click the image to play the video segment 11D.
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
WHAT MAKES MEIOSIS
DIFFERENT ?
Crossing over
Segregation
Independent
assortment
are ALL ways MEIOSIS results in
=______________________________
GENETIC RECOMBINATION
different
So daughter cells are ______________
from parents and from each other
WHAT MAKES MEIOSIS
DIFFERENT ?
3. Skip INTERPHASE II (No S)
CELL DIVIDES TWICE, BUT …
ONLY COPIES ITS DNA ONCE
MITOSIS:


1
G
S
G2  P
MEIOSIS:
G1  S


M
G2  P  M
PM

A

T C
A T C (I)
 A  T  C ( II )

Video 2
Animal Cell Meiosis, Part 1 & Part 2
Click the image to play the video
segment 11B. & C
Video 2
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Go to
Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Go to
Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Go to
Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Go to
Section:
Figure 11-15 Meiosis
Section 11-4
Meiosis I
Go to
Section:
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.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
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.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
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.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
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.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
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.
Go to
Section:
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
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
11-5 Linkage and Gene Maps
• Chromosomes assort independently, not
individual genes. The farther apart genes
are located on a chromosome, the more
likely they are not to be linked. (they are
more likely to be separated by crossingover)
• Gene maps show the exact location of a
particular gene on a chromosome.