Cell Cycle b Chapter 12~ The Cell Cycle

Cell Division: Key Roles b Genome: cell’s genetic information b Somatic (body cells) cells b Gametes (reproductive cells): sperm and egg cells b Chromosomes: DNA molecules b Diploid (2n): 2 sets of chromosomes b Haploid (1n): 1 set of chromosomes b Chromatin: DNA-protein complex b Chromatids: replicated strands of a chromosome b Centromere: narrowing “waist” of sister chromatids b Mitosis: nuclear division b Cytokinesis: cytoplasm division b Meiosis: gamete cell division

Centromere Centriols Sister Chromotides Chromosome Spindle fibers

The Cell Cycle b Interphase (90% of cycle) G1 phase~ growth S phase~ synthesis of DNA G2 phase~ preparation for cell division b Mitotic phase Mitosis~ nuclear division Cytokinesis~ cytoplasm division

Mitosis b Prophase b Prometaphase b Metaphase b Anaphase b Telophase

Prophase b Chromosomes visible b Nucleoli disappear b Sister chromatids b Mitotic spindle forms b Centrosomes move

Metaphase b Centrosomes at opposite poles b Centromeres are aligned b Kinetochores of sister chromatids attached to microtubules (spindle)

Anaphase b Paired centromeres separate; sister chromatids liberated b Chromosomes move to opposite poles b Each pole now has a complete set of chromosomes

Telophase b Daughter nuclei form b Nuclear envelopes arise b Chromatin becomes less coiled b Two new nuclei complete mitosis

Cytokinesis b Cytoplasmic division b Animals: cleavage furrow b Plants: cell plate

b The reasons that cells divide. The larger the cell the more demands the cell places on its DNA.The larger the cell the more demands the cell places on its DNA. The second reason is it has a harder time moving enough nutrients and wastes across the membrane.The second reason is it has a harder time moving enough nutrients and wastes across the membrane. b DNA doesn’t copy itself except for during cell division Why Division

Cell Cycle regulation b Growth factors- protein that helps stimulate division b Density-dependent inhibition-crowded cells stop dividing b Anchorage dependence- must be attached to something

Regulators b These help tell cells when to divide and when to stop or to not divide at all. b These are proteins that regulate cell division. They are called Cyclins. b There are 2 types of regulators internal and external growth factors. b Cancer is uncontrolled cell growth. Because it doesn’t respond to internal growth factors or external growth factors

b Internal growth factors- are proteins that respond to events inside the cell. They don’t let it divide till all the chromosomes have been copiedThey don’t let it divide till all the chromosomes have been copied Don’t let it go into anaphase until the spindle fibers are attachedDon’t let it go into anaphase until the spindle fibers are attached b External growth factors- proteins that respond to events outside the cell. Tell it to speed up or slow down the cell cycleTell it to speed up or slow down the cell cycle Growth factors stimulate cell growth and division of cells.Growth factors stimulate cell growth and division of cells. Another are molecules found on the surface of neighboring cells that tell the cell to slow down or stop dividingAnother are molecules found on the surface of neighboring cells that tell the cell to slow down or stop dividing These prevent excessive cell growthThese prevent excessive cell growth

Cancer b Transformation- change from a normal cell to cancer b Tumor: benign or malignant b Metastasis- move

Binary Fission b How prokaryotes replicate b Origin of replication