Biologia e genetica - mutazioni del genoma

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