Download Base excision repair

Base excision repair
Base excision repairs DNA
when a base of a nucleotide is
damaged, for example cytosine.
T
1
A
G
C
C
T
2
A
G
T
Cytosine can easily lose an
amino group, forming a base
called uracil.
3
T
G
A
C
G
T
A
4
T
A
G
C
G
T
A
A
U
T
C
G
G
A
Uracil cannot form a
base pair with guanine.
5
T
A
G
C
C
G
T
A
U
An enzyme, glycosylase,
discovers the defect and
excises the base of uracil.
Another couple of enzymes
remove the rest of the
nucleotide from the DNA strand.
DNA polymerase fills in the
gap and the DNA strand is
sealed by DNA ligase.
Illustration: © Johan Jarnestad/The Royal Swedish Academy of Sciences