Biologia e genetica - mutazioni del genoma

Alterazioni del DNA e riparazione

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: α, β, γ, δ, ε. 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