2. Regents Biology 2006-2007 Biology is the only subject in which multiplication is the same thing as division…

3. Regents Biology MITOSIS: Making New Cells Making New DNA

4. Regents Biology Where it all began… You started as a cell smaller than a period at the end of a sentence…

5. Regents Biology And now look at you… How did you get from there to here?

6. Regents Biology  Going from egg to baby…. the original fertilized egg (zygote) has to divide… and divide… Getting from there to here…

7. Regents Biology Why do cells divide…  One-celled organisms  for reproduction  asexual reproduction (clones)  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 amoeba starfish Binary fission regeneration

8. Regents Biology Examples of Asexual Reproduction  Binary Fission is the equal division of both the organism’s cytoplasm and nucleus to form two identical organisms  Budding involves one parent dividing its nucleus (genetic material) equally, but cytoplasm unequally yeastprotist

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11.  Sporulation (spore formation) reproduction involving specialized single cells coming from one parent

12. Regents Biology  Regeneration  Grafting

13. Regents Biology Asexual Reproduction  Advantages  Genetic continuity  Faster  Do not need a mate  Disadvantages  If environmental conditions change, may die out  Disease could eliminate the population

14. Regents Biology Dividing cells…  What has to be copied  DNA  organelles  cell membrane  lots of other molecules  enzymes animal cellplant cell

15. Regents Biology Copying DNA  A dividing cell duplicates its DNA  creates 2 copies of all DNA  separates the 2 copies to opposite ends of the cell  splits into 2 daughter cells  But the DNA starts loosely wound in the nucleus  If you tried to divide it like that, it could tangle & break nucleus cell DNA

16. Regents Biology Organizing & packaging DNA nucleus cell DNA nucleus cell 4 chromosomes in this organism DNA in chromosomes in everyday “working” cell DNA in chromosomes in cell getting ready to divide DNA has been “wound up” (chromatin)

17. Regents Biology Chromosomes of Human Female 46 chromosomes 23 pairs

18. Regents Biology Chromosomes of Human Male 46 chromosomes 23 pairs

19. Regents Biology Copying & packaging DNA Copying DNA Coil DNA into compact chromosomes  When cell is ready to divide…  copy DNA first, then…  coil up doubled chromosomes like thread on a spool…  now can move DNA around cell without having it tangle & break

20. Regents Biology What happens when DNA breaks?  Mutations which can lead to……..  Cancer – uncontrolled cell growth melanoma

21. Regents Biology double-stranded human chromosomes ready for mitosis

22. Regents Biology DNA must be duplicated… nucleus cell DNA in chromosomes nucleus cell duplicated chromosomes chromosomes in cell 4 single-stranded chromosomes duplicated chromosomes 4 double-stranded chromosomes

23. Regents Biology INTERPHASE  CELL IS GROWING  CHROMOSOMES ARE REPLICATED (COPIED)

24. Regents Biology PROPHASE 1. CHROMATIN BECOMES CONDENSED (THICKER) 2. NUCLEOLUS DISAPPEARS 3. NUCLEAR MEMBRANE DISAPPEARS 4. CENTRIOLES BEGIN TO MOVE TOWARDS THE POLES 5. SPINDLE FIBERS START TO APPEAR 6. CHROMOSOMES BECOME VISIBLE

25. Regents Biology METAPHASE CC HROMOSOMES LINE UP ALONG THE MIDDLE OF CELL

26. ANAPHASE CC ENTROMERES SPLIT ALLOWING CHROMATIDS TO SEPARATE OO NE MATCHING CHROMATID MOVES TO EACH POLE

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28. TELOPHASE AND CYTOKINESIS  CHROMATIDS AT OPPOSITE POLES  SPINDLE FIBERS DISAPPEAR  NUCLEAR MEMBRANE REAPPEARS  CYTOKINESIS: CELL DIVIDES INTO TWO GENETICALLY IDENTICAL CELLS

29. Regents Biology New “daughter” cells  Get 2 exact copies of original cells  same DNA  “clones”

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31. Cell division in Animals

32. Regents Biology Mitosis in whitefish embryo

33. Regents Biology onion root tip

34. Regents Biology KEYS TO MITOSIS  Original cell has complete set of chromosomes  This is known as DIPLOID or 2N DIPLOID  One division results in 2 DAUGHTER CELLS  No genetic material exchanged  Cells are GENETICALLY IDENTICAL  Daughter Cells are also DIPLOID or 2N  Ex. Original cell has 46 chromosomes, daughter cells will have 46 chromosomes  IN SINGLE CELLED ORGANISMS:  Method of reproduction (ASEXUAL)  Protists, some Algae, and Molds  IN MULTI-CELLED ORGANISMS:  Mitosis used for GROWTH and REPLACEMENT of BODY CELLS (skin, liver, heart etc…)

35. Regents Biology Overview of mitosis interphaseprophase metaphaseanaphasetelophase cytokinesis I.P.M.A.T.C. P lease M ake A nother T wo C ells

36. Regents Biology Basic diagram of mitosis HUMAN SKIN CELL 46Chromosomes 46Chromosomes 46Chromosomes 2 NEW HUMAN SKIN CELLS