Biology Reference
In-Depth Information
dNTPs
dNTPs
(B)
(A)
N
Legend
= DNA Lesion
N
N
= Replicative polymerase
= Extender polymerase
= Specialized polymerase
N
N
N
N
N
NNNN
N
NNNN
FIGURE 5.8
Models for the efficient bypass of DNA lesions during translesion DNA synthesis. (A) After encountering a DNA lesion,
a replicative DNA polymerase incorporates a nucleotide opposite it but is unable to extend beyond the lesion. A specialized DNA polymerase
extends beyond the lesion. Once the lesion is bypassed, the specialized polymerase is replaced by the replicative polymerase to resume proc-
essive DNA synthesis. (B) The replicative polymerase stalls at the DNA lesion and is unable to incorporate a nucleotide. In some cases,
a specialized polymerase can incorporate and then extend beyond the DNA lesion prior to being replaced by the replicative enzyme. In other
cases, one specialized polymerase is needed for insertion opposite the lesion and another specialized polymerase is required for extension.
FIGURE 8.2
Strand-break termini produced by oxidative DNA damaging agents including IR. The chemical nature of the 3
0
-termini depends
on the site of attack on the deoxyribose group.
