The Last Revision Meiosis Redux

A) A fancy dish served at Asian Fusion restaurants.
B) The name of the newest singing sensation.
C) The process by which haploid cells called gametes
are formed.
Why is meiosis important?
Just because it is.
B) It allows the chromosome number to be halved.
C) Yo no se!
What is involved in meiosis?
A) A series of steps similar to mitosis.
B) Haploid cells (gametes).
C) A lot of vowels.
D) Both A and B are correct.
What is a haploid cell?
A) A cell that is happy.
B) A sex cell—egg or sperm.
C) A cell that has half the number of chromosomes as a
somatic (body) cell.
D) Both B and C are correct.
Meiosis: The Facts
 Process resulting in formation of reproductive cells.
 Occurs using similar steps as mitosis.
 End product is 4 genetically different haploid cells.
 Haploid cells are 1C.
 Diploid cells are 2C.
 Occurs in two stages—Meiosis I and Meiosis II.
 Meiosis I – separates the tetrad resulting in TWO cells.
 Meiosis II – separates the sister chromatids resulting FOUR
Meiosis – The Cast
Homologous Chromosomes –
(AKA Tetrad)
 pairs of similar but not
identical chromosomes.
 They code for the same
 One is inherited from
mother (pink) and other
from father (blue).
Homologous Shoes?
 Look at your shoes.
 How can they compare
to homologous chromosomes?
 Sisters
 Similar but not identical
 (left and right shoes)
 All shoes (in class)
 No two pairs are identical
 Unique pairs of
chromosomes in the cells
Meosis – The Cast
 Chromatin – packed
genetic material
From oodle noodle to
bow pasta!
Meiosis – The Cast
Sister Chromatids = one
complete chromosome
1) Chromatid
2) Centromere
3) Short-Arm of
4) Long-Arm of
Meiosis – The Cast
 Tetrad –formed during
meiosis I.
 These are PAIR of sister
 Called a tetrad because
there are FOUR
chromatids present.
 “Swapping” of genetic
material between
chromosomes occurs
between tetrad.
A Tetrad of Shoes
 Two pairs of shoes = one
 Each pair of shoes = one
 Each pair = sister chromatids
 Each individual shoe =
one chromatid.
Meiosis -- Preview
 Occurs in two stages.
 Steps are very similar to mitosis.
 4 haploid cells are end product of meiosis II.
 Meiosis I and Meiosis II are similar.
 Exceptions:
DNA replication Does NOT occur in Meiosis II.
TWO cells produced after Meiosis I and FOUR cells after
Meiosis II.
From Diploid to Haploid
 Meiosis I – results in TWO cells b/c TETRAD has
been separated.
 Genetic information is “swapped” between maternal
and paternal chromatids. This is called synapse.
From Diploid to Haploid
 Meiosis II – results in FOUR cells b/c sister chromatids
have been separated.
 New cell are genetically different due to cross over.
Meiosis—Party Time!
Turkey in the CELL
Link arms – represents the
Synapse – bump hips
“crossing over”
Mosey – a cross between a skip
and a gallop
Metaphase plate – the equator
of the cell (it is the middle of
the room)
Salute – wave and bow
Meiosis I – The Nitty Gritty
 Prophase I – chromatin condense into chromosomes,
tetrads form, spindles form
 Metaphase I -- tetrads line up at the equator, spindles
attach to centromere
 Anaphase I – tetrads are pulled apart toward the
poles by spindle fibers
 Telophase I – cell splits completely producing two
daughter cells with one complete chromosome (sister
Meiosis II – The Scoop
 Meiosis II – Repeats the steps as Meiosis I with HALF
as many chromosomes
Prophase II – DNA does NOT replicate.
Metaphase II–Sister Chromatids line up at the equator.
Anaphase II – Sister chromatids are pulled toward the
poles and separate.
Telophase II – Cell splits 4 haploid cells are formed,
with 1 chromatid.
Meiosis – Cover Shot
Questions, Pictures, Autographs?
Thank You!!
Ya’ll come back now!
I hope you enjoyed the
and learned something.
 Beyonce
 Homologous Chromosomes
 Chromatin
 Chromatid
 Tetrad
 Meiosis Phases
 Meiosis vs Mitosis
 Meiosis Stain
 Waving Hands

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