Biochemistry 2280A Chapter Notes -Exonuclease, Complementary Dna, Homologous Recombination
Document Summary
To preserve genetic information, the cell must guard against unintended changes in the sequence or structure of dna, which will be referred to as dna damage. The main types of dna damage are mentioned below. Despite the proofreading ability of dna polymerase, mistakes can still occur and this can possibly lead to a change in the dna sequence or mutation in daughter dna. The amine group of a nitrogenous base, most commonly cytosine is changed to a carbonyl; occurs spontaneously and may lead to mutation; upon deamination, cytosine is converted to uracil. Acid promotes the loss of an entire adenine or guanine base resulting in an abasic site. The sugar-phosphate backbone remains intact but abasic sites block replication by the normal replicative dna polymerase. Honestly, check this in the lecture notes, this doesn"t seem like something we talked. The double bonds in adjacent pyrimidines, most commonly two thymines, react to form a cyclobutane ring; usually caused by uv radiation.