  This paper is an introduction to rational tangles, rational knots and links
and their applications to DNA. The paper can be read as an introduction to our
more technical papers on rational tangles (math.GT/0311499) and on rational
knots (math.GT/0212011). The present paper includes a self-contained account of
the tangle fraction from the point of view of the bracket polynomial, accounts
of the classification theorems for rational tangles and rational knots (and of
our new proofs of these results) and a description of the use of rational
tangles in studying DNA recombination.
