Please take out your science journal and outcomes and turn in any missing work to the WIRE basket Thank you Asexual Reproduction Review Happens in almost all cells Somatic cells 1 parent cell ID: 513484
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Slide1
Sexual Reproduction and Meiosis
Please take out your science journal and outcomes and turn in any missing work to the WIRE basket. Thank you!
Slide2
Asexual Reproduction Review
Happens in almost all cells (Somatic cells)
1 parent cell
Cell divides into 2 exact genetic copies with 46 chromosomes each
Stages are:
interphase
mitosis
Cytokinesis (2 cells formed)
Needed for:
growth and development
cell replacement
asexual reproduction of new organisms
regeneration Slide3
Sexual Reproduction Preview
Happens ONLY in sex cell formation (gametes)
2 parent cells called gametes
with ½ the original chromosomes (23 in humans
) are needed to create a new cell with mixed genetic code
How are they created?
Stages are
Interphase
4 stages of “mitosis” (meiosis I)
4 stages of “mitosis” AGAIN (meiosis II)
Cells split (4 gamete cells formed with ½ the of the original chromosomes)
Needed for genetic diversity and creating new organisms, both plant and animalSlide4
Meiosis
How do the gametes only end up with half of the chromosomes?
This takes place during meiosis.
Meiosis is cell
division that produces reproductive cells in sexually reproducing organisms
(plants and animals).
Meiosis VideoSlide5
Before Meiosis
Each chromosome duplicates like they did in interphase of mitosis.
Now the cell will go through 2 cycles of meiosis dividing the cell
twice
.
In mitosis, the chromosomes separated and moved away from each other.
In meiosis, the separation is different.Slide6
Meiosis I
First stage of meiosis:
Prophase I =
copied
chromosomes
go
close
their
duplicate.
Metaphase I =
2 pairs
of chromosomes line up in the
center of the cell as in mitosis.Anaphase I = Each pair of chromosomes does NOT separate from each other but move away from the other pair.Telophase I = cytoplasm divides creating 2 new cells, each with one original and one duplicated chromosomeSlide7
Meiosis II
Prophase II = 2 cells have 2 duplicated chromosomes from Meiosis I
Metaphase II = Chromosomes line up in middle of each cell
Anaphase II = Chromatids separate and move to each end of each cell.
Telophase II = Nucleus reforms around each individual chromosome.
4 new cells have formed, each with ½ the number of chromosomes.Slide8
Meiosis pg 128-129Slide9
Meiosis under the MicroscopeSlide10
Meiosis Summary
2 cells form during meiosis I
Each of these cells form 2 cells in meiosis II
4 sex cells are created with ½ the chromosomes that were in the original nucleus
I humans 1 cell with 46 paired chromosomes results in 4 cells with 23 unpaired chromosomesSlide11
Meiosis Practice
Bats have 44 chromosomes in 22 pairs in their somatic cells. How many chromosomes are in each sex cell?
22 unpaired chromosomes
Dandelions have 24 chromosomes
in
12 pairs in their
somatic cells
.
How many chromosomes are in
each
sex
cell?
12 unpaired chromosomesKing crab have 208 chromosomes in 104 pairs in their somatic cells
.
How many chromosomes are in
each
sex
cell?
104
unpaired chromosomes