Biochemistry review (continued)

Biochem review (contiued)
Albinism Defect in tyrosine-> melanin converting Tyrosine 3-monooxygenase (tyrosinase) defect UV-> DNA cross linkage-> thymine thymine dimer Protective clothing, sunglasses, sunscreen is necessary!! HNPCC (Hereditary nonpolyposis colon cancer) Laning p.970 One of the most common inherited susceptibility of getting cancer. Cause: defects in mismatch repair. If > 5 different mismatch repaire genes impair, HNPCC could happen. Most common: hMLH1 (human MutL homolog 1) and hMSH2 (human MutS homolog 2) genes MutL and MutS are genes in bacteria for mismatch repairment. Replication of DNA Semiconservative; Bidirectional Direction:5'-3' (leading strand) 3'-5'(lagging strand) Tool: DNA polymerase (leading) Okazaki fragment (lagging) ² DNA Polymerase I : special functions while replicating, recombination, repairing (such as ligase for fulfilling gaps, excising primers) ² DNA Polymerase II: restart of DNA replication and repairment ² DNA Polymerase III: primary replication enzyme ² RNA Polymerase I: makes ribosomal RNA ² RNA Polymerase II makes mRNA ² RNA Polymerase III makes small RNAs such as transfer; 5S and others. Accuracy of replication by l Polymerase base selection l 3'-5' proofreading exonuclease l After replication mismatch repair system Polymase—DNA dependent RNA polymerase for RNA primer making Reverse transcriptase—RNA dependent DNA polymerase Sequence of gene repair system Recognition->Nicking->excision->replacement (DNA polymerase I)->sealing ( ligase) `