Depurination can produce transversion mutations

    (1) In the original intact dsDNA molecule, G pairs with C. (2) In one ssDNA strand, hydration of the bond between the base and the sugar leads to the loss of the G base (depurination), while leaving the sugar-phosphate backbone intact. (3) When this strand is replicated, DNAPol copies the 'blank' apurinic position by incorporating a random base (in this example, A) in the newly synthesized strand. (4) Replication of that strand  replaces the original G / C pair with a T / A pair. The result is a G T  transversion mutation.

[HOMEWORK: Can random base incorporation at an apurinic site give rise to a transition mutation? Explain why or why not, using the above example].

    Depurination in intact dsDNA is ordinarily repaired in vivo by proof-reading polymerases. DNA in non-living forensic or palaeontological material is not subject to repair, and the accumulation over time of apurinic sites prevents such 'ancient DNA' (aDNA) material from being correctly read by the polymerase chain reaction.

All text material © 2011 by Steven M. Carr