1. The Cell Cycle, Mitosis and Meiosis
Cell Reproduction

2. The Cell Cycle
Most of a cell’s time
not spent dividing
G 1: Gap 1 or Growth1: cell is growing after just being created
S stands for Synthesis. DNA is copied before the cell can divide again
G2 is a second growth stage as the cell prepares to divide again

3. Mitosis is used to….
Mitosis is used for asexual reproduction. To spread out in a habitat by making clones.
It is also used to grow and develop and repair injuries

4. This is a clone of Aspen Trees. They are all genetically identical

5. There are 4 Steps to Mitosis, and Interphase when cells
are in the G, S and G2 parts of the cell cycle

6. sister chromatids During the S part of the Cell cycle, the DNA
Replicates
This creates two identical
pieces of DNA called
sister chromatids
Together the two sisters
Make up a chromosome

7. Prophase (First phase)
Occurs as the
chromosomes become
visible and the nuclear membrane begins to
break down.

8. During Metaphase
(middle phase)
The Chromosomes
Line up in the middle of
The cell. Having been
Pushed and pulled on
By the spindle fibers
Spindle Fibers

9. Each sister chromatid attaches to
different spindle fibers at the
Kinetochores of the chromatids

10. During Anaphase (Separate)
The spindle fibers shorten, pulling
the sister chromatids apart to opposite
ends of the cell. Once apart they are now
each called Chromosomes.

11. Telophase (End phase)
Two nuclei reform, and a new cell wall called a cell plate is built in plants to separate the cytoplasm of the two new daughter cells.

12. The two daughter cells are identical
to each other and to the parent
cell which created them

13. Egg and sperm cells (gametes) need one half the chromosomes of the
Mitosis works fine for
Growth and development
Repair of damaged tissue
But it can’t be used to make egg or sperm cells because…
Egg and sperm cells (gametes) need one half the chromosomes of the
parent cell

14. Meiosis Sexual Reproduction in Plants
Meiosis makes cells with 1/2 of the chromosomes as the parent cell.
In plants this process makes either male microspores that become sperm, or female megaspores that become eggs
This process also makes unique cells

15. In plants a diploid (two sets of
Chromosomes) generation
Does meiosis to make a
haploid (half the number of
Chromosomes) generation.

16. Homologous Chromosomes
Pairs of chromosomes that control the same traits

18. During Meiosis the cell goes through two divisions
In the first one, the homologous cells separate, and in the second the sister chromatids separate
Creating up to 4 cells with half the number of chromosomes as the parent cell.

19. How does Meiosis create unique cells?
During Prophase 1 crossing over happens to the homologous pairs to create new combinations of DNA

20. Unique cells due to crossing over
Homologous pair
One from mom, one from dad
Crossing
Over
Unique cells due to crossing over