BIOLOGY Unit 4 Notes: Mitosis

(1) What is Mitosis? Cell division for non-sex cells. Non-Sex Cells: Are also called Somatic Cells. Examples Skin, Hair, Muscle, Bone, etc.

(2) What happens during Mitosis? Cells make exact copies of themselves. Start with 1 cell, and end up with 2 identical copies. Start “2n” or “Diploid”  End “2n” or “Diploid” 2n = Diploid = Full set of genetic information In Humans this means a full set of 46 chromosomes (or 23 pairs).

(3) Mitosis & DNA DNA is a very long molecule. In order to make it easier to move around inside the cell, the DNA molecule is condensed first into “Chromatin” and then “Chromosomes”. Chromosomes = Wound up DNA = Look like fingers

(4) Sister Chromatids Remember: Before Mitosis, the cells go through Interphase of the Cell Cycle (G1, S, and G2). The DNA has to be copied so each new cell has its own. (DNA is copied during the S Phase.) The resulting copies of DNA or Chromosomes are called “Sister Chromatids”. Sister Chromatids: Identical chromosomes with the same genes.

(5) Basic Steps in Mitosis Condense DNA into chromosomes. Line up pairs of Sister Chromatids in the center of the cell. (This helps to organize the DNA and make sure the cell correctly divides up the copies.) Separate the Sister Chromatids. Divide the cell parts. End Result = 2 Identical Cells