1. Growth, Repair, and Reproduction
Mitosis and Meiosis
Growth, Repair, and Reproduction

2. Some vocabulary to know
Somatic cell: a body cell having the full complement of Chromosomes (humans = 46)
Diploid: having the full complement of chromosomes, both members of each pair (2N)
Gamete: a sex cell, like egg, sperm, pollen, having only one of each of the paired chromosomes from an organism. (humans =23)
Haploid: having half the complement of chromosomes, one of each pair (1N)

3. Mitosis
Purpose: to produce new cells for growth or repair of body tisuse.
Triggered when cell gets too large, or when cell senses a space nearby (like in a cut).
Outcome: 2 daughter cells that are identical clones of original somatic cell.
In humans: one cell with 46 chromosomes produced 2 daughter cells each having 46 chromosomes.

4. The Stages of Mitosis
As interphase ends, cell is large and has duplicated its DNA. The DNA strands are holding onto their copies.
PROPHASE: chromosomes holding onto their copies become visible, nuclear membrane dissolves
METAPHASE: chromosomes line up at middle of the cell, spindle fibers connected to centromeres
ANAPHASE: spindle fibers separate each chromosome form its copy, pulling the copies to opposite poles
TELOPHASE: reverse of prophase: nuclear membrane reforms, chromosomes loosen and become less visible

5. Meanwhile back at the gonads….
Mitosis will occur, but certain cells will be triggered to continue into meiosis to form sex cells.

6. Crossing Over occurs in Meiosis
Crossing Over increases diversity in species , it mixes up the genes that came from your parents so the same traits don’t always get inherited together.

7. The steps of Meiosis

8. The result: 4 haploid cells

9. Fertilization recombines the chromosomes
2N-a zygote!

10. A new life begins again with mitosis…

11. Ob-La-Di, Ob-La-Da…