 Which
animal will stay
warm longer, a mouse or
an elephant?
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
Define in your own words (p. 275)
Meiosis
Diploid
Haploid
Gamete
Crossing Over
Chromosomes
2
 Draw
a chromosome. Explain
what a chromosome is.
 Why is crossing over
important?
3


All eukaryotic cells store genetic
information in chromosomes
Human body cells have 46 chromosomes or
23 identical pairs
4

Two sides of a
chromosome are
called
chromatids &
are held
together by the
centromere
Called Sister Chromatids
5
Chromosomes contain DNA and
Protein packed together to form
chromatin.
 Chromatin is made of DNA that is
wrapped around the protein,
histones.
 Histone and DNA forms clusters
called nucleosomes.

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The Y Chromosome Decides
Y - Chromosome
X - Chromosome
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 Explain
the differences
between homologous
chromosomes and sister
chromatids.
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9
10



Two meiotic divisions --- Meiosis
I and Meiosis II
Original cell is diploid (2n)
Four daughter cells produced that
are haploid (1n)
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Sister
chromatids
separate
Homologs
separate
Meiosis
I
Meiosis
II
Diploid
Diploid
Haploid
12
Spindle
fibers
Nucleus
Early
Prophase I
(Chromosome
number
doubled)
Late
Prophase
I
Nuclear
envelope
Metaphase
Anaphase Telophase I
I
I
(diploid)
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 Before
Meiosis Begins
Nucleus
 DNA replication occurs
14
 Crossing over occurs- homologous
chromosome- Form Tetrad
15
Homologous chromosomes
(each with sister
chromatids)
Join to form a
TETRAD
16

Pieces of
genes are
exchanged
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1. Crossing-over occurs during:
A. anaphase 1
B. Metaphase 1
C. Prophase 1
D. Prophase 2
2. Which of the following cells undergo
meiosis?
A. Sperm Cells
B Liver Cells
C. Unicellular organisms
D. All of the above
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Explain all parts of a chromosome, in
words and drawings.
 Define diploid, chromatin,
sister chromatids, and centromere.
 Extra Credit: What phase is
technically not part of meiosis?
Why?

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Homologous pairs
of chromosomes
align along the
equator of the
cell
21
Homologs separate and
move to opposite poles.
Sister chromatids remain
attached at their
centromeres.
22
 What
is the difference
between Metaphase and
Anaphase?
 What is the job of the
centrioles?
23
Nucleus reassembles.
Spindle fibers disappear
Cytokinesis divides cell
into two.
24
 What
is the difference
between Interphase and
Prophase?
25
 Explain
what occurs in
Meiosis I, in your own
words.
26
Gene X
Only one homolog of each
chromosome is present in
the cell.
Sister chromatids carry
identical genetic
information.
Meiosis II produces gametes with
one copy of each chromosome and
thus one copy of each gene.
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Prophase
II
Metaphase
Telophase
II
Anaphase
4 Identical
II
II
haploid cells
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Nuclear envelope
disappears.
Spindle forms.
Half the number
of chromosomes as
original in each
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 What
is the difference
between Prophase I and
Prophase II?
 What is the difference
between the cells at the end
oogenesis and
spermatogenesis?
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 At
the very end of meiosis
II each cell has 23
chromosomes.
 How
many chromosomes are
created during Interphase?
 How many chromosomes does
the cell have at the very start of
Prophase I?
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Chromosomes align
along equator of cell.
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Equator
Pole
Sister chromatids
separate and
move to opposite
poles.
33
 What
is the difference
between Anaphase I and
Anaphase II?
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Nuclear envelope
assembles.
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Gametes (egg & sperm)
form
Four haploid cells with
one copy of each
chromosome
Different combinations
of different genes
Hybrid offspring
36
Meiosis results in _____
A. 2 haploid daughter cells
B. 4 haploid daughter cells
C. 2 diploid daughter cells
D. 4 diploid daughter cells
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The picture depicts what stage of
meiosis?
A. Prophase 1
B. Anaphase 1
C. Metaphase 1 D. Metaphase 2
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 Egg:
Oogenesis
Formation of 1 true egg
and 3 polar bodies
 Sperm: Spermatogenesis
Formation of 4 true sperm
cells
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
Make an information pamphlet about one specific genetic
diseases.
 The following must be included:
 What is the disease? What does the disease do to the body
it is affecting?
 When was the disease discovered? Who discovered it?
 What type of mutation causes the disease?
 What are the tests to see if a person has the disease?
 How many people get this disease?
 Any other important information people need to know
about the disease.
 Pictures
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Friday December 19, 2008
Bring some food to share with the class. It can
be anything you enjoy!
If you don’t bring something you
can’t eat anything!
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