Notes

CYTOSKELETON Part II
MATERIAL COVERED UP TILL FRIDAY LECTURE -not monday-

GTPase activity: (ase usually means catalyzation) - so catalyzation of GTP Hydrolysis (GTP breakdown)
-> Important for this dynamic disability

Chain of monomers: any monomer that binds to the polymer is a GTP monomer (in the polymerization or growing state) -> It has GTPase activity when it joins the polymer (begins hydrolyzing from GTP to GDP)

i.e. Chain: D-D-D-D-T-T <--- T (Cap is the string of T's at the end). If the cap is hydrolyzed, then the cap is removed before we could polymerize more (if hydolization of GTPs are faster, then cap is removed)

CATASTROPHE-Was growing, and now the cap is lost (accidental)
The polymer will shink rapidly (RESCUE)
The GTP cap will be regained and rapid growth with GTP capped end will continue

The higher the concentration of GTP bound monomers, you are more likely to have several binding at one time (High concentratio of T's, more likely to grow)

GTP conformation is straight (stable)
GDP conformation is slightly bent (unstable and wants to polymerize)

GTP bound growing monomers are straight, while shrinking polymer looks like string cheese

Dynamic Instability in vivo -
the growing/shrinking (fluctuating length) the ability to fluctuate length (reconfigure cytoskeleton)
-> important because it can reshape the cell for different reasons

Probing all over the cell (if you want to change the shape or behavior of the cell, Any microtubule that sticks out can reshape the cell

Microtubule is the most ancient motor activity

CELL CYCLE & CELL DIVISION
-Cell is the fundamental unit of life
-> Cells must be able to reproduce
Replicate DNA and make copies of genomes
-> Cells must grow and duplicate genome and segregate everything from daughter cells as well

-If there is too many or too less organisms, the amount doesn't matter too much
-However genes are very important to segregate equally (so that daughter cells have the right genetic information)
-Bacteria are very efficient at replication and division

In Eukaryotes (there is replication, wait, and segregation)

M phase: division
G1/2 Phases: Gap phases (wait)

Division, Wait at G1, Replication in S Phae, Wait again, Division,etc.
Cells have to decide when to move on with the phases )when they are done dividing/replicating

Fission Yeast Cell as a model system
-Yeast are unicellular (simple) and are similar to us (eukaryotic model)
-Want to have rapid cell cycle (divides quickly)

Grows-gets longer- divides (cut in half)-cytokenisis
If you are haploid you only have 1 chromosome, you don't ahve two chromosomes

If you make mutations of certain genes, how do you affect the cell cycle. Haploid genome has a huge advantage to the study discussed
HAPLOID: 1 copy of each gene
Introduce mutations at random and observe affects
-> specifically wanted to focus how the phase transitions were controlled

Growth in G2 phase: Checks if cells grew too long without replicating

Procedure to find large cells: but didn't find them. Instead he found mutants that were too small (wee mutant)
-wee1
-cdc2 (cell division cycle 2) was the name of the mutation
-How is the cell cycle regulated in humans (is there a gene that creates a protein with the same function of cdc2)

Human genes were transformed into the yeast cells (looked to see if there was any gene from the human genome that would ring the cells back to their normal size)
Found that there are genes (human CDC2) that were able to rescue cell size

AMINO ACID SEQUENCE
Hs: Homo Sapiense
-Amino acids are quite identical among the three species (conservative)
-CDC2 protein must have an important function

-CDC2 encases a Kinase