Mitosis notes outline Why cells divide 1. DNA G1, S, G2 2. Diffusion 3. SA/volume ratio 4. repair Cell division A. Chromatin vs. chromosome (picture and parts) B. Stages (include pictures 1. interphase G1, S, G2 2. mitosis prophase metaphase anaphase telophase 3. cytokinesis animal vs. plant cell END RESULT=

*Living things grow because they produce more cells. Cell Growth *Living things grow because they produce more cells. *Rather than grow indefinitely, cells divide into new cells because it is more efficient for the cell. WHY???

Factors that limit cell growth: 1. amount of DNA: *cells remain small so DNA can meet all of the cell’s needs 2. exchange of materials through the cell membrane ex. water, food, oxygen, waste products

surface area to volume ratio: surface area = 6(length x width) volume = (length x width x height) ratio = surface area volume *cells need high surface area for small volume for materials to easily enter/exit the cell *volume increases faster than surface area thus decreasing the ratio and causing problems for the cell

cell division: process by which a cell divides into two new daughter cells *done before a cell becomes too large so the cell is more efficient. Solves problems mentioned: each cell gets DNA, reduces volume Also used to repair and replace old cells

Cell Division *Cells must copy their genetic information before cell division to ensure daughter cells have a complete copy. Where is genetic info. (DNA) found in a cell? in nucleus packaged as chromosomes (usually exists as chromatin)

*all cells have a specific number ex. humans—46 carrots—18 Chromosomes: *all cells have a specific number ex. humans—46 carrots—18 fruit flies—8 *before division, chromosomes are replicated (an exact copy is made) sister chromatids: two identical halves of chromosome Centromere: holds sister chromatids together Sister chromatids Centromere

Duplicated chromosome Chromosomes Sister chromatids Unduplicated Chromosome Duplicated chromosome

cell cycle: series of events that cells go through as they grow and divide Stages of cell cycle: 1. interphase: period of growth 2. mitosis: division of cell nucleus 3. cytokinesis: division of cytoplasm

Cell Cycle Events: I. Interphase:> 75% of time spent here, normal cell activities occur 3 phases: 1. G1: cell grows, synthesizes proteins and organelles 2. S: DNA (chromosomes) replicated 3. G2: organelles needed for division are produced

II. Mitosis 4 phases: 1. prophase: *longest phase of mitosis *chromosomes become visible *spindle fibers develop *nucleolus disappears *nuclear envelope breaks down

2. metaphase: *chromosomes line up in the middle (equator) of cell

3. anaphase: *centromere splits * shortest phase of mitosis *sister chromatids separate (become individual chromosomes) and move apart

4. telophase: *chromosomes uncoil into chromatin *nuclear envelope re-forms around chromatin *spindle disappears (break apart) *nucleolus becomes visible *opposite of prophase

III. Cytokinesis= division of cytoplasm *occurs at the same time as telophase animal cells: cell membrane is drawn inward until the cytoplasm is pinched into two nearly equal cells

plant cells: cell plate develops into a separating membrane; cell wall appears along cell plate

End result of Cell Cycle Two new daughter cells that are genetically identical to each other and the parent cell.

Mitosis Prophase Metaphase Anaphase Telophase

Section 8.2 Summary – pages 201 - 210 Results of Mitosis Click image to view movie. Section 8.2 Summary – pages 201 - 210