Introduction to Genetic Analysis 460

Introduction to - 44200_14_p451-480 1:06 PM Page 459 14.1 Point mutations 459 H3C N N N N H Guanine H 6 1NH CH2 O 6 1N O N EMS N O H N3 H O 1 CH3

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
459 14.1 Point mutations helix (Figure 14-10b). In this intercalated position, an agent can cause single-nucleotide-pair insertions or deletions. BASE DAMAGE A large number of mutagens damage one or more bases; so no speci±c base pairing is possible. The result is a replication block, because DNA poly- merase cannot continue DNA synthesis past such a dam- aged template base. In both prokaryotes and eukaryotes, such replication blocks can be bypassed by inserting non- speci±c bases. In E. coli , this process requires the activa- tion of the SOS system. SOS and other mechanisms of biological repair will be described later in this chapter. However, an overview of this repair mechanism will be presented in this section because, somewhat ironically, some repair mechanisms are themselves responsible for mutating DNA. The name SOS comes from the idea that this system is induced as an emergency response to pre- vent cell death in the presence of signi±cant DNA dam- age. As such, SOS induction is a mechanism of last
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

Ask a homework question - tutors are online