Lecture 11 Topics Cell Biology 9-17-01 Chapter 6 p.242-265

Unit Evolutionary time: Time for 1% acceptable amino acid changes

30% of deaths in 1^st world = cancers (grossly disproportionate attention vs. 3^rd world misery)

Chances of dying in agony are very high

Essential proteins max roughly 60,000 for germline stability (cancer problem for somatic cells)

DNA repair essential: nuclease, polymerase, ligase

Base excission-repair+ nucleotide excission-repair are 2 major processes

Note: alterations of cytosine yields uracil, so, no uracil in DNA

SOS response in E. coli = Mutate its way out of a "fix". Rec A intimately involved (lambda use)

DNA replication: polymerase can't start from scratch, add to free 5' OH

Leading and lagging strands. Okazaki fragments. Sliding clamp, SSBP, replicating fork.

Unmethylated DNA = "wrong"

Replication origin = "bubble"

DNA helicases, topoisomerases, etc.

general and site-specific recombination