Regents Biology Cell Cycle – Interphase + Mitosis  Interphase – where the cell spends most of its time  G1, S, G2  Doing GRRSNERT  Mitosis – cell division  PMAT  Making new cells  Making new DNA IPMAT

Regents Biology  Going from egg to baby…. the original fertilized egg has to divide… and divide… Getting from there to here… Fertilized egg = zygote Levels of organization: cells tissues organs organ systems

Regents Biology Why do cells divide…  One-celled organisms for reproduction  asexual reproduction (clones) – binary fission  Examples: paramecia, amoeba  Multi-celled organisms  for growth & development  from fertilized egg to adult  for repair & replacement  replace cells that die from normal wear & tear or from injury Cells MUST remain small to be efficient amoeba starfish Regeneration – part of an organism

Regents Biology In Dividing cells…  What has to be copied  DNA - instructions to make proteins  organelles  cell membrane - made of lipids and proteins  lots of other molecules  Enzymes –  Type of protein animal cellplant cell

Regents Biology Forms of DNA  Chromatin  Chromosomes  Chromatids 4 single-stranded chromosomes Unwound DNA DNA wound or coiled Replicated DNA – held together by centromeres 2 chromosomes – count centromeres 4 chromatids

Regents Biology DNA must be duplicated… nucleus cell DNA in chromosomes nucleus cell duplicated chromosomes Start with 2n OR diploid chromosomes Two of each “kind” – pairs of homologous chromosomes Carry similar information STILL have 2n or diploid chromosomes – but have chromatid copies # chromosomes = # centromeres

Regents Biology  Same size and shape  Similar “banding pattern”  In sexual reproduction – one from each pair comes from each parent Homologous Chromosomes - Pairs of chromosomes that carry similar genetic info

Regents Biology Before Mitosis: Interphase  G1/S/G2: cell copies DNA, makes organelles, GRRSNERT  MOST time spent in this phase doing the cell’s “job” nucleus One 2n diploid cell DNA (Chromatin) Copy DNA! (interphase)

Regents Biology Mitosis: PROPHASE  Prophase: DNA winds into chromosomes  DNA is wound up into chromosomes to keep it organized so they are visible  Nuclear membrane starts to break down nucleus one 2n diploid cell duplicated chromosomes Wind up! (prophase)

Regents Biology Mitosis: METAPHASE  Metaphase: chromosomes line up in middle  Along the “equator”  attached to protein “spindles” that will help them move to opposite “poles” Line up! (metaphase) Spindle fibers Poles – centrioles in animal cells; asters in plant cells

Regents Biology Mitosis: ANAPHASE  Anaphase: Chromatids separate  centromeres duplicate, homologous chromatids split, separating chromatids  start moving to opposite ends or poles Separate! (anaphase)

Regents Biology Mitosis: TELOPHASE (including cytokinesis)  Telophase: Cell starts to divide  nuclei form again in two new cells  Followed by cytokinesis – division of cytoplasm  animal cell membrane “pinches” in  plant cell forms a cell plate that becomes the cell wall Divide! (telophase)

Regents Biology Interphase (again)  DNA unwinds; cells separate  now they can go back to doing their every day jobs - GRRSNERT  cycle starts over again two 2n diploid cells 2 new smaller “daughter” cells  Get 2 exact copies of original cells  same DNA  “clones”

Regents Biology Mitosis in whitefish embryo

Regents Biology Mitosis in plant cell

Regents Biology onion root tip

Regents Biology

Overview of Cell Cycle interphase prophase metaphaseanaphasetelophase cytokinesis I.P.M.A.T.C. P lease M ake A nother T wo C ells

Regents Biology When is mitosis a BAD thing  When cells reproduce & they are not needed  these cells take over organs, but don’t do the right job  they just keep making copies  “starve” other cells/tissues  cancer – uncontrolled mitosis  damages organs

Regents Biology Why would cells just make copies?  If DNA gets damaged, cells stop listening to correct instructions – make WRONG protein (enzymes)  mutations – changes in DNA bases  Mutagens (carcinogens) – cause mutations:  UV radiation  chemical exposure  benzene, toluene, asbestos  radiation exposure  cigarette smoke  pollution  age  Genetics  heat

Regents Biology Tumors  Benign tumor  abnormal cells remain at original site as a lump  most do not cause serious problems & can be removed by surgery

Regents Biology Tumors  Malignant tumor  cells leave original site - metastasizes  carried by blood system to other tissues  start more tumors  damage functions of organs throughout body

Regents Biology Treatments for cancers  Treatments kill rapidly dividing cells  chemotherapy  poisonous drugs that kill rapidly dividing cells  radiation  high energy beam kills rapidly dividing cells  surgery side effects