ABSTRACT
When foreign DNA is introduced into a bacterium, it is usually unable to perform any genetic functions. One reason for this is that bacteria have evolved efficient means to protect themselves from invading DNA. A group of enzymes known as restriction endonucleases or restriction enzymes perform this function by cleaving the DNA, thus "restricting" the activity of the invading DNA. The bacteria's own DNA is protected from its arsenal of restriction enzymes by another class of enzymes that modifies or methylates the host DNA. This chapter describes some mathematical problems that arise in connection with making maps of the locations of restriction sites. Restriction maps show the location or approximate location of a selection of restriction sites along linear or circular DNA. The study of interval graphs has its origin in a paper of Benzer in 1959 who was studying the structure of bacterial genes.
