Ability of DNA to repair itself

[axlenatore]

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Ok ive got different information from three sources. Hsc onlin, my teacher and another biology teacher have told me different things.

My biology teacher said the following
[FONT='Cambria','serif']Enzymes can remove damaged parts of DNA
1. Endonucleases open up the DNA
2. Exonucleases remove one base at a time
3. DNA polymerase adds one base at a time
4. Ligases joins the new section to close the gap

Another Biology teacher who took us while my teacher was sick and originally taught us this (she is a regular biology teacher)
[FONT='Cambria','serif']Mutations are not as rare as first thought and when mistakes occurs various repair mechanisms are initiated
1. Revmoes damaged DNA (restiction enzymes cut it out)
2. Replaces damage/inncorrect bases (enzyme- polymerase)
3. New section is joined to old (enzyme-ligase)

HSC online says the following
DNA replicates every time a cell undergoes mitosis for growth and repair or meiosis for gamete production. This continues to occur throughout the life of the organism. Mutations or mistakes in the copying of the DNA are common and cells contain mechanisms to repair these mistakes. Copying errors can be repaired by enzymes such as DNA polymerase that can use the undamaged strand of DNA in the double helix as a template to fix and replace the incorrect damaged base sequence.

They all agree that enzyme-polymerase adds the correct base sequence but which actually removes the old seqeunce[/font][/font]

[homijoe]

this is wat i have:

nuclear excision is a form of dna repair, whereby a nuclease enzyme cuts the damaged strand at two points. repair synthesis then takes place by dna polymerase and then ligase enzymes fill the remaining nick..

[alez]

shit. i never did this. my bio teacher left the school and kinda gave up and didnt care for the last couple months he was there
so if there is a mutation or error, the dna will unzip by the action of an enzyme, similar to dn replication. The incorrect bases are removed and replaced by free nucleotides. Is that right?
how does the body recognise the mutations though?