Chapter 10:Mitosis

Cell Growth and Division

Cell Division

• Cell Division – cell divides into two new IDENTICAL “daughter cells”

• Mitosis – division of nucleus during eukaryotic cell division

• Cytokinesis – division of cytoplasm during eukaryotic cell division

Cell Cycle

Interphase

• Interphase – portion of cell cycle between divisions– ~ 75 – 80% life of cell– 3 phases:

• G1: cells grow and develop

• S: chromosomes replicate

• G2: organelles required for division reproduce

Chromosome

• Chromosome – located in nucleus– contains DNA

• Chromatid – half of chromosome

that has been replicated

– pair of “sister” chromatin

• Centromere – area where each pair of

chromatids attach (in center)

CHROMOSOMECHROMOSOME

centromerecentromere

sistersister chromatidchromatid

sistersister chromatidchromatid

MitosisProphase Metaphase Anaphase Telophase

“Please Make Another Test”• 1. Prophase

– doubling of chromosomes & organelles – centrioles visible

• 2. Metaphase – chromosomes line-up in the middle – spindles from centrioles connect to each chromatid (half of chromosome)

• 3. Anaphase – chromatids are pulled apart to separate ends– membrane begins to pinch off in the middle

• 4. Telophase– Nucleus and nuclear envelope reform– Chromosomes decondense and disappear (you can no longer see them)– Cytokinesis - complete division of cytoplasm – two daughter cells formed

Prophase -DNA condenses into chromosomes

-Nuclear membrane begins to break down- centrioles & chromosomes visible

Metaphase - chromosomes line-up in the middle

- spindles from centrioles connect to each chromatid

Spindlemicrotubules that help separate chromosomes

Anaphase - chromatids are pulled apart to separate ends- membrane begins to pinch off in the middle

Telophase-Each set of chromosomes is positioned at each end

of the cell-Chromosomes begin to uncoil & spindles far apart

- two daughter cells formed

Cytokinesis- cells “pinch” off from one another

- cytoplasm divides

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120073/bio14.swf::Mitosis%20and%20Cytokinesis

Regulating the Cell Cycle• Cyclins

– Proteins that stimulate division during growth and repair (Interphase)

– Internal regulators • respond to the events inside the cell

– External regulators • speed up or slow down the cell cycle

Cancer

• Cancer = uncontrolled cell growth– do not respond to signals that regulate growth

– causes: heredity, chemicals, radiation

• Tumors = unregulated cell growth – Benign: cells stay together

– Malignant: cells spread and grow elsewhere

- invade healthy tissues