Biochemistry 2280A Lecture Notes - Lecture 16: Homologous Recombination, Xeroderma Pigmentosum, Dna Ligase
15 Oct 2017
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Document Summary
To preserve genetic information, the cell must guard against unintended changes in the sequence or structure of dna, which i will refer to as dna damage . The main types of dna damage are mentioned below: copying mistakes. Despite the proofreading activity of dna polymerase (see topic. 15), mistakes occur during dna replication, at a rate of about 1 per 107 nucleotides in humans. The result is one or more mismatched base pairs, which would lead to a change in the dna sequence, or mutation, in one of the daughter double helices after. Acid promotes the loss of an entire adenine or guanine base, resulting in an abasic site (fig 6-23a, p. 212). Abasic sites block replication by the normal replicative dna polymerase. Dna polymerase stalls, one of several translesion dna polymerases is recruited to the site. After a translesion polymerase has synthesized dna past the site of damage, the normal replicative dna polymerase resumes dna synthesis: deamination.
