Mitosis

Cell Theory… States that all cells come from preexisting cells. Cell Division – The process where new cells are produced from one cell. Result of Cell Division – 2 cells that are identical to the parent (original) cell. Bonus Question: What must our DNA do to create new cells?

Chromosomes… Right before we undergo cell division we create chromosomes in our nucleus. Chromosomes are DNA that has been tightly coiled around proteins, and looped and coiled even further. Why do you think DNA undergoes all this trouble before division?

Chromatids Chromatids – what we call the final DNA product. This is copied and the copies stay attached to each other. Centromere - what keeps the two copies attached to one another. (In middle)

Diploid… Any cell containing 23 pairs (46 total) chromosomes. The pairs are almost identical meaning they have the same genes in the same order. All cells except sex cells are diploid.

Haploid… Any cell that contains only 23 chromosomes (no pairs). Examples: mature sex cells such as sperm and eggs. Why do our sex cells only need 23 chromosomes instead of 46 (23 pair)?

Types of Chromosomes… Gametes – sex cells (egg, sperm) Autosomes – What we call the 22 pairs of chromosomes that do no deal with determining the sex of the person. (Pairs 1-22). Sex Chromosomes – 1 pair (pair 23) the determines the sex of the person.

X and Y… There are 2 types of sex chromosomes possible, X and Y. Females are XX Males are XY Women only produce eggs with X. Men produce sperm with both X and Y. Who determines the sex of a baby? The mother or the father?

Karyotypes… You have already seen 2 karyotypes by now. These are images where the chromosomes have been sorted by size and shape and arranged into their pairs. Of the two karyotypes which one is male, and which is the female? A or B.

Person A

Person B

Eukaryotic Cell Cycle… Interphase - the cell is taking in food, growing, replicating DNA and copying its organelles. 3 Stages: G1 Phase – Intense cell Growth. Cell spends most time here. S Phase – duplicate chromosomes. Create Sister chromatids connected by a centromere. G2 Phase – continues to Grow and duplicate organelles.

Mitosis… In cell cycle called the M Phase. 4 Phases to Mitosis. Prophase – DNA coils making chromosomes, the nuclear envelope breaks open, spindle fibers are made, and the centrioles split going to the poles of the cell.

Prophase…

2nd Phase of Mitosis Metaphase – chromosomes attach to the spindle fibers and line up in the middle.

3rd Phase of Mitosis Anaphase – The sister chromatids get separated at the centromere and 1 heads in each direction.

4th Phase of Mitosis Telophase – Now each side of the cell has a complete set of chromosomes, the nuclear envelopes begin to form around them. The spindle fibers disappear and the centrioles deactivate.

Cytokinesis… Takes place after mitosis. It is the division of the rest of the cell where organelles are split up and the cytoplasm divides in half. Cell becomes 2 cells.

Cell plates… In plant cells a new cell wall begins to form between the 2 nuclei and eventually creates 2 different cells.

Cleavage Furrow… The cell membranes in an animal cell come together and the cell pinches off into 2 separate cells like bread dough being divided in two.

Division continued… Cells can usually only divide up to 50 times before they die. Not all cells can do this. Nerve cells can never divide. Stem cells divide many more times and become any type of cell in the entire human body. Proteins keep the cell cycle in check by activating cyclines to stimulate different phases, or by not activating them due to DNA damage.