Cell Division

Mitosis and Meiosis

The Cell Cycle

Mitosis

Interphase

Cell Growth

Prior to mitosis, the cell is in Interphase Interphase is a time where

The cell grows Organelles replicateDNA is copied

Most of a cells life is spent in interphase

Mitosis

Occurs in body cells (somatic cells)

Results in 2 daughter cells identical to the parent cell

4 phases: prophase, metaphase, anaphase, and telophase

Prophase

Stage 1 of Mitosis DNA winds up to form chromosomes Nuclear membrane (membrane around the

nucleus) disappears

Metaphase

Stage 2 of Mitosis Chromosomes line up at equator (center) of

the cell

Anaphase

Stage 3 of Mitosis Chromosomes split - each half is pulled to

opposite sides of the cell

Telophase

Stage 4 of Mitosis Nuclear membranes form around each set of

chromosomes and the chromosomes unwind to form strands of DNA

Cytokinesis

After mitosis occurs, the cells must split - this process is called cytokinesis

There are two methods - one for cells without a cell wall, like animal cells, and one for cells with a cell wall, like plant cells

Cytokinesis - No Cell Wall

The membrane starts to pinch inward, between the two nuclei

It will continue to pinch, until the cell splits into two new cells

Cytokinesis - Cell Wall

Cell forms a cell plate between the two nuclei

This cell plate provides foundation for new cell wall

Membranes form inside cell walls, and end up with two daughter cells

Meiosis - Formation of Sex Cells

Occurs in sex cells (eggs and sperm)

Results in 4 daughter cells Each with HALF the DNA of the parent cell All are different from one another AND parent

Split into two Stages, each with 4 phases

Prophase I

DNA winds up into chromosomes Nuclear membrane disappears

Metaphase I

Chromosomes line up at equator Line up next to homogolous chromosome

(e.g. chromosome 1 from dad lines up next to chromosome 1 from mom)

Anaphase I

One chromosome from each pair is pulled to opposite sides of the cell

Telophase I & Cytokinesis

Nuclear membrane forms around each set of chromosomes

Chromosomes may unwind Cells split

Prophase II

Nuclear membrane disappears Chromosomes wind up

Metaphase II

Chromosomes line up at equator

Anaphase II

Chromosomes split, each half pulled to opposite sides of the cell

Telophase II & Cytokinesis

Nuclear membrane reforms around each set of chromosomes

Chromosomes unwind Cells split

Compare Mitosis/Meiosis

2 cells formed

Daughter cells identical to parent cell

Occurs in body cells

4 phases

4 cells formed

Daughter cells have 1/2 DNA of the parent cell

All 4 are different

Occurs in sex cells

8 phases/2 stages

ProphaseMetaphaseAnaphaseTelophase

Cells divide