Mitosis

Growth Increase in size-more cells Cells possess internal controls over the process of cell division. Each cell knows it’s size limitation. Some cells like skin cells divide continuously Heart and nerve cells reach a certain size, stop growing and rarely divide

CELL SIZE- How big can a cell get? 2 Factors limit cell size 1. DNA- can only control so much of the reactions within the cell(DNA contains instructions for protein manufacturing) 2. Surface Area vs. Volume- the cell volume increase faster than the surface membrane. Cell can’t make enough membrane fast enough. SA increases to the 2nd power while volume increases to the 3rd power

CELL REPRODUCTION-MITOSIS Results in formation of 2 identical daughter cells Also called body or SOMATIC cells Need to replicate cytoplasm and all of the organelles- including the chromosomes(coiled chromatin) Chromatin- thin, uncoiled chromosomes and proteins called histone

Chromosome number Each species has a certain set number of chromosomes- ½ from mom, ½ from dad. Humans have 46 or 23 pairs. Each chromosome contains genes that determine all the attributes of that organism from eye color to protein synthesis.

CELL CYCLE sequence of growth and division 2 STAGES 1.Interphase 2. A Mitosis :replication of nuclear material Prophase Metaphase) Anaphase Telophase 2.B. Cytokinesis

Interphase :G1-S-G2 G1-growth and development S- DNA replication and important proteins produced G2- new organelles and more RNA produced

1. INTERPHASE Growth period Normal chromosome number- 46(23 pairs) When CD is about to happen: the chromosomes duplicate- now have 92

2.PROPHASE Longest phase Chromatin coils up Sister chromatids pair up (original and copy) Nuclear membrane and nucleolus disappear Centrioles migrate to ends Spindle forms(microtubules).Help pull chromatids apart. Other mt radiate out from pole- called asters. Original and copy held together by centromere

CENTROMERE

3. METAPHASE Shortest phase Sister chromatids line up in the middle(equator)

4. ANAPHASE Chromosomes begin to separate with help of spindle fibers

5. TELOPHASE Chromosomes reach opposite ends Nuclear membrane begins to reform around each set of chromosomes Chromosomes begin to loosen and return to chromatin Cell has 2 nuclei

6. CYTOKINESIS Division of cytoplasm Cell membrane reforms End up with 2 identical cells In plant cell- division of material along cell plate-becomes cell wall.

CONTROL OF CELL GROWTH Accomplished by proteins called CYCLINS and enzymes They must bind together in order to become active

Cancer Uncontrolled growth of a cell Caused by : change in enzyme production or environmental cause which causes a change in the gene which leads to a protein change This gene change causes uncontrolled growth which is now called cancer. The mass can grow large enough and deprive normal tissue of nutrients. Sometimes a cell from the mass breaks off and travels to other body part through the circulatory system (Metastasis)

Types of Cancer Malignant- disease causing Benign- no malignant

Cancer Causes Genetic(born with faulty gene) Environmental- sunlight, smoking, chemicals Viral infection- causes destruction of gene ( ex. Cervical cancer)