The Cell Cycle

entering cell division

cells that come out of cell division

G1- cell grows (1 chromatid) S - replicates DNA (creating sister chromatids) G2 - final growth stage (2 chromatid - sister)

• Mitosis (DNA separates aka sister chromatids) • Cytokinesis (cells separates)

Joined identical copies of original chromosomes, created by DNA replication

→ every piece of DNA gets duplicated so daughter cells have same sets of chromosomes

Microtubules which pull the sister chromatids apart during mitosis - spindles extend from centromeres!!

connect proteins at the centromere, position chromosomes in center of cell and then pull apart (attach to chromosomes, manipulating the chromosomes) - attach to chromosomes

overlap, instead of connecting to chromosomes, they connect to microtubules at other ends of the cell. Help set up the cells pinching away from each other (attach to other microtubules, lengthening the cells as it splits apart) - attach to other microtubules

1) Prophase 2) Pro-metaphase 3) Metaphase 4) Anaphase 5) Telophase/Cytokinesis

division of the genetic material

• chromosome condense • spindle forms

• nuclear envelope fragments • microtubules attach to chromosomes and each other

• chromosomes line up in middle

• sister chromatids separate • cell elongates (microtubules stop getting longer, start getting shorter, change from push to pull)

• Daughter nuclei form • chromosomes condense • cell pinches off to form two cells

Stained cells are suspended in liquid and passed through a laser beam. If the fluorescent markers have been attached to the cells, they will emit light at specific wavelengths Fluorescence signal = amount of DNA in the cell

BrdU staining →fluorescent signal of each cell will be proportional to the amount of DNA prescient.

control point where stop and go signals can regulate the cell

surveillance - is DNA damaged? - are chromosomes aligned properly?

growth/stimulus - sufficient nutrient - growth factors present? - enough space?

decides if there is a need for the cell to divide Most responsive to external signals ex. Enough nutrients, space, signaling molecule (growth factors) etc

Internal signals, is it ok for the cell to divide, has the DNA been damaged

metaphase to anaphase transition during mitosis Internal signals have all the chromosomes been connected to both sides, are they lined up correctly