Mitosis Unit 5 What is Mitosis Mitosis is

Mitosis Unit 5

What is Mitosis? • Mitosis is the division of the nucleus • This is how we get new cells from existing cells

Limits to Cell Growth • There are two reasons cells divide rather than continue to grow: 1. The larger the cell becomes, the more demands the cell places on its DNA 2. Larger cells have more trouble moving enough nutrients and wastes across the cell’s membrane

1. DNA “Overload” Cell Demands DNA s u cle Nu This is like a normal cell

1. DNA “Overload” Cell Demands DNA s u cle Nu + This is like a stressed out cell that needs to divide

Exchanging Materials TOWN LIMIT (Cell membrane) This is like a normal cell

Exchanging Materials TOWN LIMIT (Cell membrane) This is like a stressed out cell that needs to divide

Division of the Cell • Cells divide before they get too large. • The process by which cells divide into two “daughter” cells is called cell division. This is like each new town getting it’s own “genetic library”!

The Cell Cycle • During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which begins the cycle again. • There are 4 phases: 1. 2. 3. 4. G 1 phase S phase G 2 phase M phase

Cell increases in size, synthesizes new proteins and organelles

Chromosomes are replicated and DNA synthesis takes place

Usually the shortest phase. Many of the organelles and molecules required for cell division are produced

Mitosis is further divided into 4 phases and cell division occurs at the end

4 Phases of Mitosis 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

Prophase • Longest part of Mitosis -60% of the time) • Chromosomes become visible • Centrioles near the nuclear envelope move toward opposite poles • Condensed chromosomes become attached to spindle fibers at their centromeres • Nucleolus disappears and the nuclear envelope breaks down (50

Metaphase • Chromosomes line up across the center of the cell (metaphase plate) • Microtubules connect the centromeres of each chromosome to the two poles of the spindle

Anaphase • Centromeres split • Sister chromatids separate toward spindles on opposite sides of the cell

Telophase • Once distinct chromosomes begin to disperse into a tangle of dense material • Nuclear envelope re-forms around each cluster (2) of material • Spindle breaks apart • Nucleolus visible in each daughter nucleus • Mitosis is complete

End of Mitosis. What’s Next? • What we’ve got: – 2 nuclei with duplicate chromosomes in the cytoplasm of a single cell • Final task: – Divide the cytoplasm

What is division of the cytoplasm called? • The division of the cytoplasm is called cytokinesis

Cytokinesis • In animal cells the cell membrane draws inward and is pinched off forming two separate cells • In plants, a cell plate forms between the nuclei, turns into a separating membrane and eventually a cell wall http: //www. youtube. com/watch? v=Vl. N 7 K 1 -9 QB 0 http: //www. youtube. com/watch? v=s 4 Pa. Oz 7 e. WS 8