La DNA Polimerasi può commettere errori Nei batteri: 1 errore ogni 10 9 basi in ogni generazione
La correzione delle bozze
Le basi si possono alterare spontaneamente
Correzione delle Bozze n2
Alterazioni del DNA indotte da agenti fisici
Alterazioni da Agenti Chimici
Il DNA danneggiato viene riparato
Due sistemi di riparazione
Le DNA polimerasi sono tante Mammalian Cells*αβ†β† γδε Polymerization: 5′ → 3′+++++ Exonuclease proofreading activity: ‡ 3 → 5′−−+++ Synthesis from: RNA primer+−−+? DNA primer+++++ Associated DNA primase+−−−− Sensitive to aphidicolin (inhibitor of cell DNA synthesis)+−−++ Cell location: Nuclei++−++ Mitochondria−−+−− * Yeast DNA polymerase I, II, and III are equivalent to polymerase α, β, and δ, respectively. I and III are essential for cell viability. † Polymerase β is most active on DNA molecules with gaps of about 20 nucleotides and is thought to play a role in DNA repair. ‡ FEN1 is the eukaryotic 5′ → 3′ exonuclease that removes RNA primers; it is similar in structure and function to the domain of E. coli polymerase I that contains the 5′ → 3′ exonuclease activity.
Malattie ereditarie legate a difetti della riparazione del DNA
Classificazione del DNA Eucariotico Protein-coding genes Solitary genes Duplicated and diverged genes (functional gene families and nonfunctional pseudogenes) Tandemly repeated genes encoding rRNA, 5S rRNA, tRNA, and histones Repetitious DNA Moderately repeated DNA (mobile DNA elements) Transposons Viral retrotransposons Simple-sequence DNA (Satellite DNA: eg telomeres) Long interspersed elements (LINES; nonviral retrotransposons) Short interspersed elements (SINES; nonviral retrotransposons) Unclassified spacer DNA
Classificazione del DNA Eucariotico
Genomi a Confronto
Struttura “tipo” di un Cromosoma Umano