Now, because there are many different possibilities that a DNA sequence can consist of, we have many, many different types of restriction enzymes that exist in nature. And each and every one of these restriction enzymes basically cleaves along a DNA molecule at a specific location on that double stranded DNA molecule. Now, many of these enzymes, in our study of these restriction enzymes, we realized that many of these restriction enzymes actually cut at palindromic sequences along that doublestrand the DNA molecule. And to see what we mean by a palindromic sequence of DNA, let's take a look at the following diagram. So, let's suppose we have a section, a palindromic section of our double stranded DNA. So remember, in any double stranded DNA molecule we have two single strands that run antiparallel with respect to one another.