Mitosis

GrowthIncrease in size-more cellsCells possess internal controls over the

process of cell division. Each cell knows it’s size limitation.Some cells like skin cells divide continuouslyHeart and nerve cells reach a certain size,

stop growing and rarely divide

CELL SIZE- How big can a cell get? 2 Factors limit cell size1. 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-MITOSISResults 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 numberEach 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-G2G1-growth and

developmentS- DNA replication

and important proteins produced

G2- new organelles and more RNA produced

1. INTERPHASEGrowth periodNormal chromosome

number- 46(23 pairs)When CD is about to

happen: the chromosomes duplicate- now have 92

2.PROPHASELongest phaseChromatin coils upSister chromatids pair up(original and copy)Nuclear membrane and nucleolus disappearCentrioles migrate to endsSpindle forms(microtubules).Help pull

chromatids apart. Other mt radiate out from pole- called asters.

Original and copy held together by centromere

CENTROMERE

3. METAPHASEShortest phaseSister chromatids

line up in the middle(equator)

4. ANAPHASEChromosomes begin

to separate with help of spindle fibers

5. TELOPHASEChromosomes reach

opposite endsNuclear membrane

begins to reform around each set of chromosomes

Chromosomes begin to loosen and return to chromatin

Cell has 2 nuclei

6. CYTOKINESISDivision of cytoplasmCell membrane reformsEnd up with 2 identical

cells

In plant cell- division of material along cell plate-becomes cell wall.

CONTROL OF CELL GROWTHAccomplished by proteins called CYCLINS

and enzymesThey must bind together in order to become

active

CancerUncontrolled growth of a cellCaused 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 CancerMalignant- disease causingBenign- not malignant

Cancer CausesGenetic(born with faulty gene)

Environmental- sunlight, smoking, chemicals

Viral infection- causes destruction of gene ( ex. Cervical cancer)