Cell Division

Why do cells divide? So that multicellular organisms can grow from one cell. So that cells can reproduce for growth & repair.

How? Asexual reproduction – reproduction involving one (or a) parent cell Cell division – a type of asexual reproduction where one cell divides and becomes two identical copies of itself. Mitosis – a special part of cell division where the nucleus of the cell makes a copy of itself and then divides into two new nuclei.

Cell Division Math If a cell divides once a day, how many cells will there be in one week (7 days)? One month? 7 days: 64 1 month: 1,073,741,824

The Cell Cycle foldable Directions are on the board. Should be completed in the composition book.

Warm up Biology is the only science in which multiplication means the same thing as division. Copy this statement on your warm up sheet. We will answer it at the end of the lesson Take out your Cell Cycle foldable (should be in your composition book).

Interphase Cell grows Chromosomes are copied Chromatids – the two chromosome copies Centromere – region where chromatids are held together

Chromosomes

Mitosis Mitosis – process of cell division that forms two new nuclei, each of which has the same number of chromosomes. 4 phases: Prophase Metaphase Anaphase Telophase

Mitosis (Prophase) Prophase = chromosomes pair up with their “twin”. Chromosomes twist, coil & condense into an “X” shape Spindle fibers form Nuclear membrane begins to break down

Mitosis (Metaphase) Nuclear membrane disappears Chromatid pairs line up in the middle of the cell metaphase = middle

Mitosis (Anaphase) Chromatids separate Move apart to opposite sides of the cell anaphase = apart Cell becomes stretched

Mitosis (Telophase) Two nuclear membranes form around each set of chromosomes telophase = two new nuclear membranes Mitosis is over

Cytokinesis Cells without a cell wall (ex: animal cells): Cell pinches in two Cells with a cell wall (ex: plants): A cell plate forms between the two new cells

Demo of Mitosis See “Cells Alive” video/demo http://cellsalive.com/mitosis.htm