Introduction to Genetic Analysis 462

Introduction to Genetic Analysis 462 - 44200_14_p451-480...

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

View Full Document Right Arrow Icon
Ultraviolet light generates a number of distinct types of alterations in DNA, called photoproducts, from the word photo for “light.” The most likely to lead to muta- tions are two different lesions that unite adjacent pyrim- idines in the same strand. These lesions are the cyclobu- tane pyrimidine photodimer and the 6-4 photoproduct. For the cyclobutane pyrimidine dimer, ultraviolet light stimulates the formation of a four-membered cyclobutyl ring (shown in green in Figure 14-12a) between two ad- jacent pyrimidines on the same DNA strand by acting on 5,6 double bonds. The 6-4 photoproduct structure (Figure 14-12b) forms between the C-6 and C-4 posi- tions of two adjacent pyrimidines, most prevalently 5 9 -CC-3 9 and 5 9 -TC-3 9 . The UV photoproducts signi±- cantly perturb the local structure of the double helix. These lesions interfere with normal base pairing; hence, induction of the SOS system is required for mutagenesis. The incorrect bases are inserted across from UV photo-
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