To: Mr. Patrick De Geest:
I note you are interested in palindromes.

There is a general feeling that palindromes are frivolous curiosities in number theory which find no real world applications other than in recreational games. This is not true. The very building blocks of life, i.e. DNA sequences, make use of palindromes. A DNA sequence consists of two complementary strands coiled in a double helical structure. DNA researchers found that some enzymes have the ability to recognise palindromes and cut DNA-sequences at these specific sites. Does this qualify Nature as the first user of palindromes ? A typical staggered cut made by an enzyme in a double helix is shown in figure 1:

                staggered cut made by
                restriction enzymes

---GAATTC--  --G!         AATTC-----------
---CTTAAG---     ---CTTAA   ! G----------

\================== Fig.1 =========================/
DNA researchers have found many such enzymes for different types of staggered cuts based on the recognition of palindromic pairs. They are now able to cut and splice DNA sequences almost at will thus contributing greatly to the present phenomenal progress in this discipline. Note that in figure 1, after the staggered cut, the two ends will each have a free stub sticking out. These free stubs will look for palindromic stubs to dock in a biochemical soup full of DNA fragments. Remember, palindromes are unique pairs.
Dr Huen Y.K. (email) from CAHRC. SINGAPORE.