The Cell Cycle Mitosis & Cytokinesis
Why do living things grow? This baby king penguin grows because he produces more and more cells.
How do cells know when to quit dividing? Cell growth and cell division are CAREFULLY controlled. Only certain cells are allowed to divide rapidly. –Ex. Hair follicles & stomach lining.
Experiment on Cell Growth
One experiment using cells in a petri dish showed that they stopped dividing when they touched! But……
That’s not always the case… Liver Cancer cells Breast cancer cell
SCARS-why do they look different? Scar Tissue is not of the same quality as unscarred skin. It is less capable of resisting ultraviolet radiation. It will not regrow hair follicles. It will not regrow sweat glands.
Mitosis The process where the nucleus is divided into two new, IDENTICAL, nuclei.
During the early stages of Mitosis… The chromatin (DNA + Proteins) becomes condensed and you can see the chromosomes.
Supercoiling cont. Histones- Special proteins the DNA coils around. Nucleosomes- A coiled, beadlike structure of DNA wrapped around a histone.
Chromosomes Chromosomes contain highly supercoiled strands of DNA. p. 225 in your book shows supercoiling
A Chromosome *Two sister CHROMATIDS Make up the chromosome *The CENTROMERE, a sticky Spot in the middle of the Chromosome, keeps the sister Chromatids together.
The Cell Cycle- I,P,M,A,T & Cytokinesis Read pages Write down what parts make up the cell cycle.
Interphase p. 228 A long period between cell divisions. 3 phases G1, S, G2 –G1, Cell grows –S, DNA doubles –G2, Organelles double