1. Intro to Cell Division Honors Bio

2. Why do cells divide? If they get too big –Surface area to volume ratio, etc. Growth of organism –In order for an organism to grow, it needs more cells Repair –New cells replace old/damaged ones Reproduction –ASEXUAL- offspring is identical to parent –SEXUAL- offspring is a combo of both parents

3. Cell Division Mitosis –Occurs in somatic cells (body cells) –Daughter cells are exactly like parent –Diploid 2n In humans n=23 Meiosis –Produces gametes (germ cells/sex cells) –Daughter cells have half the chromo- somes as parent “Reduction division” –Haploid 1nWhy?

4. DNA LINGO Chromatin- –when a cell is not dividing it’s DNA is a tangled mass of thin threads. Chromosome- –When the DNA is ready to divide it condenses into individual chromosomes In humans- there are 23 HOMOLOGOUS PAIRS of chromosomes The two chromosomes in a pair are SIMILAR but not exactly alike One is from mom and one from dad Sister Chromatid- –When the DNA replicates (to make one copy for each cell) the two copies join together by a centromere and each copy is called a SISTER CHROMATID –These sisters are EXACTLY ALIKE!

8. The cell cycle (somatic cells) INTERPHASE –growth and preparation G1SG2MITOSIS –Nucleus divides ProphaseMetaphaseAnaphaseTelophaseCYTOKINESIS –Division of cytoplasm