Cell Reproduction: Ch. 9

9.1: Growth…What is it? Getting larger Making more Division/ mitosis (eukaryotes) Binary Fission (prokaryotes)-budding

Reasons for Division: 1.) Growth (large size)-cells must be small Communication between proteins and DNA Transport of substances (slow over large area) Let enough nutrients diffuse in (surface to volume ratio) 2.) Repair (cell replacement) 3.) Healing

Chromosomes: Rod shaped structure made of DNA and proteins Condensed chromatin Helix coil of DNA A chromosome has 2 identical sides called chromatids The middle of the “x” is called the centromere Sex chromosomes: X and Y (determine F or M)

Three Steps in Cell Cycle 1.) Cell Cycle Cell grows and copies chromatin 90% of time 2.) Mitosis- 4 steps of nuclear division (chromatin splits) 3.) Cytokinesis- division into two new cells

Mitosis: 9.2 Complex and delicate processes Mitosis: Divides DNA into 2 identical nuclei Cytokinesis: Splits cytoplasm to form 2 identical “daughter” cells 2 Diploid cells (46 chromosomes)

DNA copying Chromosomes need to be copied into every new cell This gives the instructions to the cells Copied chromosomes are called sister chromatids Joined at centromere

Prophase (1 st step) Nuclear Envelope disappears Chromosomes are visible. Centrioles and spindle fibers move to the poles

Metaphase (2 nd step) Chromatids line up at the equator Spindle fibers are connected to the centromere.

Anaphase (3 rd Step) The sister chromatids pull apart.

Telophase (4 th step) Nuclear envelop re-forms Chromosomes uncoil Cell plate starts to form (plant cells)

Cytokinesis Cytokinesis and Telophase take place at approximately the same time. Where mitosis is the division of the nucleus, cytokinesis is the division of the cytoplasm. Animals Cells: pinch at cleavage furrow Plant Cells: new cell wall formed on cell plate

9.3: Cell Cycle and Cancer Cell Cycle: 1.) Interphase: -G1: Growth (cytoplasm) -S: Synthesis of DNA Chromosomes copied -G2: Growth

Continued… 2.) Mitosis: Divide nucleus/ DNA 3.) Cytokinesis: Divide cytoplasm

Control of the Cell Cycle: Signals: Cyclins (chemicals) These bind to enzyme kinases (receptors) to move ahead at each step

Continued… Almost every step has a “quality control” checkpoint”

Control of the Cell Cycle: Contact inhibition: Cells stop dividing when they get crowded Chemicals signal this

Cancer: Cancer is an uncontrolled cell cycle Problem with enzyme Disruption of contact inhibition signal Can be caused by many things: Carcinogens: tobacco, uv, x-rays, pollution Genetics, Age

Continued: Tumors: Mass of cancerous tissue It deprives normal cells of nutrients

Cancer Fighters: Apoptosis: Programmed death for old or damaged cell Chemo and radiation can influence this process Stem Cells: “Good Originals” Differentiate into many different cell types 2 types: Embryonic (controversial) Adult (hard to use)