DNA (Deoxyribonucleic acid) carries all of the genetic information.
DNA is a linear string (polymer) of four different units or base
pairs labelled A, C, G and T. These can be thought of as the
letters of the genetic code. These base pairs in turn spell the
words (called the genes) of the genetic code.
A gene is the hereditary determinant of a characteristic (like
eye color.) The human genome (all of the information in a single
human cell) is estimated to contain between 50,000 and 100,000
genes. Cells are normally dividing to copy themselves and replenish
cells which have died. Each cell contains 3 billion base pairs
(A, C, G and T.)
So, every time a cell divides it must copy all 3 billion base
pairs. Unfortunately, cells can make mistakes when copying this
DNA. If one of these mistakes is made in a gene that prevents
pancreas cancer, then that person will be at increased risk for
developing pancreas cancer.