DNA uses error detection and correction
Example: DNA is extremely sensitive to UV radiation
- If a photon strikes a thymine base that borders another thymine
- it forms a thymine photodimer T<>T
- and halts enzymatic reaction on the DNA
- If the cell doesn’t fix the flaw, it will die
Enzymes fix T<>T flaws
- UV endonuclease cleaves the sugar-phosphate backbone at the T<>T
- Other enzymes remove a block of several thousand nucleotides
- Kornberg’s DNA polymerase rebuilds the strand
- Using the second strand as a template