Transcript Meiosis TEACHER

Cellular
Division
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Cell Division
All cells are derived from pre-
existing cells
New cells are produced for
growth and to replace damaged or
old cells
Differs in prokaryotes (bacteria)
and eukaryotes (protists, fungi,
plants, & animals)
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Identical Daughter Cells
Two
identical
daughter
cells
Parent Cell
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Chromosomes
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Prokaryotic Chromosome
The DNA of
prokaryotes
(bacteria) is one,
circular
chromosome
attached to the
inside of the cell
membrane
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Chromosomes in Dividing Cells
Duplicated
chromosomes are
called
chromatids &
are held
together by the
centromere
Called Sister Chromatids
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Karyotype
A picture of the
chromosomes from
a human cell
arranged in pairs by
size
First 22 pairs are
called autosomes
Last pair are the
sex chromosomes
XX female or XY
male
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Cell Reproduction
https://www.youtube.com/
watch?v=9nsRufogdoI
Mitosis and Meiosis song
3:50min.
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Types of Cell Reproduction
Asexual reproduction involves a
single cell dividing to make 2 new,
identical daughter cells
Mitosis & binary fission are
examples of asexual reproduction
Sexual reproduction involves two
cells (egg & sperm) joining to make a
new cell (zygote) that is NOT
identical to the original cells
Meiosis is an example
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Cell Division in Prokaryotes
 Prokaryotes such as
bacteria divide into 2 Parent
cell
identical cells by the
process of binary
fission
Chromosome
 Single chromosome replicates
makes a copy of
itself
 Cell wall forms Cell splits
between the
chromosomes dividing
the cell
2 identical daughter cells
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Animation of Binary Fission
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The Cell
Cycle
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Five Phases of the Cell Cycle
G1 - primary growth phase
S – synthesis; DNA replicated
G2 - secondary growth phase
collectively these 3 stages are
called interphase
M - mitosis
C - cytokinesis
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Cell Cycle
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Interphase - G1 Stage
1st growth stage after cell
division
Cells mature by making more
cytoplasm & organelles
Cell carries on its normal
metabolic activities
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Interphase – S Stage
Synthesis stage
DNA is copied or replicated
Two
identical
copies
of DNA
Original
DNA
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Interphase – G2 Stage
2nd Growth Stage
Occurs after DNA has been copied
All cell structures needed for
division are made (e.g. centrioles)
Both organelles & proteins are
synthesized
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What’s Happening in Interphase?
What the cell looks like
Animal Cell
What’s occurring
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Sketch the Cell Cycle
DNA Copied
Cells
Mature
Daughter
Cells
Cells prepare for
Division
Cell Divides into
Identical cells
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Mitosis
https://www.youtube.com/watch
?v=VlN7K1-9QB0
1.29..MIN. ANIMATION…
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Mitosis
Division of the
nucleus
Also called
karyokinesis
Only occurs in
eukaryotes
Has four stages
Doesn’t occur in
some cells such
as brain cells
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Four Mitotic Stages
Prophase
Metaphase
Anaphase
Telophase
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Spindle Fiber attached to
Chromosome
Kinetochore Fiber
Chromosome
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Review of Prophase
What the cell
looks like
What’s
copyright happening
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Sketch The Spindle
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Review of Metaphase
What the cell looks
like
What’s
occurring
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Anaphase
Sister
Chromatids
being
separated
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Anaphase Review
What the
cell looks
like
What’s
occurring
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Comparison of Anaphase & Telophase
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Cytokinesis
Cleavage furrow
in animal cell
Cell plate in
plant cell
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Daughter Cells of Mitosis
Have the same number of
chromosomes as each other and as
the parent cell from which they
were formed
Identical to each other, but smaller
than parent cell
Must grow in size to become mature
cells (G1 of Interphase)
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Identical Daughter Cells
What is
the 2n
or
diploid
number?
2
Chromosome number the same, but cells
smaller than parent cell
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Draw & Learn these Stages
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Draw & Learn these Stages
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Eukaryotic Cell Division
 Used for growth and
repair
 Produce two new cells
identical to the original
cell
 Cells are diploid (2n)
Prophase
Metaphase
Chromosomes during
Metaphase of mitosis
Anaphase Telophase Cytokinesis
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Mitosis Animation
Name each stage as you see it occur?
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Mitosis in Onion Root Tips
Do you see any stages of mitosis?
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Test Yourself
over Mitosis
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Identify the Stages
?
Early, Middle, & Late Prophase
?
?
Metaphase
Late Prophase
Late Anaphase
Anaphase
?
?
Telophase
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?
?
Telophase &
Cytokinesis
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Locate the Four Mitotic
Stages in Plants
Anaphase
Telophase
Metaphase
Prophase
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Uncontrolled Mitosis
 If mitosis is not
controlled, unlimited
cell division occurs
causing cancerous
tumors
 Oncogenes are special
proteins that
increase the chance
that a normal cell
develops into a tumor
cell
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Cancer cells
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https://www.youtube.com/wa
tch?v=JcZQkmooyPk
MITOSIS…..6.20 MIN.
10 FACTS!!!!!!
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Meiosis
Gamete Production
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Meiosis
Similar in many ways to mitosis
Several differences however
Involves 2 cell divisions
Results in 4 cells with 1/2 the
normal genetic information.
Vocabulary:
Diploid (2N) - Normal amount of
genetic material
Haploid (N) - 1/2 the genetic
material.
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Meiosis
 Meiosis results in the formation of
haploid cells.
In Humans, these are the Ova (egg)
and sperm.
Ova are produced in the ovaries in
females
Process is called oogenesis
Sperm are produced in the testes
of males.
Process is called spermatogenesis
 Meiosis occurs in 2 phases: Meiosis I
& Meiosis II
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Spermatogenesis & Oogenesis
Sperm
formation
Egg
formation
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Meiosis I
 Prior to division (S phase), amount of
DNA doubles
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Metaphase I
 During Metaphase I
homologous
chromosomes lineup along the
metaphase plate or
EQUATOR
 Areas of
homologous
chromosomes
connect at areas
called CHIASMATA
 Genes are
exchanged at
these connections
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Crossing Over
 Segments of
homologous
chromosomes
break and
reattach at
similar
locations.
 Results in new
genetic
combinations of
offspring.
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Crossing-Over
Crossing-over multiplies the already huge
number of different gamete types
produced by independent
assortment
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Chiasmata
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Anaphase I
 During Anaphase I, each
HOMOLOGOUS
CHROMOSOME is pulled to
opposite sides of the cell.
 Unlike mitosis, the
CENTROMERES DO NOT
BREAK.
 Nuclei MAY OR MAY NOT
reform following division.
 CYTOKENESIS may or may
not occur.
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Meiosis II
 DNA DOES NOT double
 Chromosomes randomly line-up
along metaphase plate like
regular mitosis.
 During Anaphase II,
CENTROMERES BREAK and
each SISTER CHROMATID is
pulled to opposite sides of the
cell.
 Nuclei reform and cytokinesis
usually occurs (although it is
often unequal).
Sister chromatids
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Meiosis: Two Part Cell
Division
Sister
chromatids
separate
Homologs
separate
Meiosis
I
Meiosis
II
Diploid
Diploid
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Haploid
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Overview of Meiosis
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Meiosis Animation
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https://www.youtube.com/wa
tch?v=16enC385R0w
BOZEMAN…..8.25 MIN.
10 FACTS !!!!!!!
https://www.youtube.com/wa
tch?v=rqPMp0U0HOA
Meiosis..crossing over 6:45
10 facts!!!!!
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Comparison of Divisions
Mitosis
Meiosis
2
Number of
divisions
1
Number of
daughter cells
2
4
Yes
No
Same as parent
Half of parent
Where
Somatic cells
Germ cells
When
Throughout life
At sexual maturity
Genetically
identical?
Chromosome #
Role
Growth and
repair
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Sexual reproduction
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