Chromosomes in Metaphase

Chromosomal Mutations

Quiz Draw a Chromosome in Metaphase and label the main parts. List Chromosomal Mutations. What factors generate mutations? Ex.

CELL DIVISION

THE PURPOSE OF MITOSIS and MEIOSIS EUKARYOTES: GROWTH AND REPAIR OF OLD/DAMAGED CELLS PROKARYOTES: REPRODUCTION (TO MAKE IDENTICAL OFFSPRING) MEIOSIS: MOST EUKARYOTES: FOR SEXUAL REPRODUCTION: CREATING SEX CELLS THESE SEX CELLS WILL BE GENETICALLY DIFFERENT. THIS INCREASES A SPECIES’ ADAPTABILITY=potential for evolution Mitosis occurs in somatic cells: any cell in the body that’s not a sex cell Meiosis occurs in reproductive cells like the ovary and testes.

CELL DIVISION: PROKARYOTES (creates new identical organism) Circular DNA makes a copy of itself Cell continues to grow until about twice its original size Cell wall forms between to chromosomes

CELL Division: Eukaryotes MITOSIS: somatic cells For growth of organism Repair of damaged cells MEIOSIS: sex cells For sexual reproduction (creation of sex cells)

THE CELL CYCLE INTERPHASE: Time between cell divisions. It includes G1, S, and G2. CELL DIVISION: Includes Mitosis (M phase) and Cytokinesis

CELL CYCLE G1:cell grows to mature size S: DNA is copied G2: Cell prepares for cell division *G0: Cells don’t copy their DNA & don’t prepare for division. Example: nerve cells stop dividing (nerve damage is permanent) http://www.cellsalive.com/cell_cycle.htm

MITOSIS Division of the nucleus into two identical nuclei (Mitosis is not cell division but first step in process) Without mitosis, cell division would result in an uneven amount of chromosomes per cell---bad!!! (information lost) 4 steps: Prophase, Metaphase, Anaphase, and Telophase (PMAT)

MITOSIS STEPS SUMMARY Prophase: Copied DNA coils until visible Nuclear envelope disappears Spindle fibers form Metaphase: Chromosomes line up in the middle Anaphase: Chromatids separate to opposite sides Telophase: A new nuclear envelope forms around each new cell http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#

Cytokinesis Animal cells: Cell pinches inward creating a cleavage furrow until two cells are created Plant cells: A cell plate forms in the middle and then the cell divides http://www.cellsalive.com/mitosis.htm

Meiosis The creation of sex cells (gametes) like sperm and egg Reduces the number of chromosomes by half Has two cell division steps that result in 4 genetically different chromosomes!!!!! (Here’s where evolution kicks in!)

How does meiosis create genetically diverse sex cells? Independent assortment: Chromosomes from mom or dad can go to whichever cell and don’t necessarily go together. Crossover: Homologous chromosomes trade off information, bits and pieces move http://www.cellsalive.com/meiosis.htm