Scientists complete first chapter of book of life with decoding
of chromosome An international team of researchers has achieved
a scientific milestone by unraveling for the first time the
genetic code of an entire human chromosome. Reported in this
week's issue of Nature (Dec. 2), researchers at the Sanger
Centre near Cambridge, England; University of Oklahoma, Norman,
OK; Washington University, St. Louis, MO; and Keio University in
Japan have succeeded in deciphering the sequence of the 33.5
million "letters," or chemical components, that make up the DNA
of chromosome 22. This sequence includes the longest, continuous
stretch of DNA ever deciphered and assembled. It is over 23
million letters in length. Each human gene is made up of a
series of chemical building blocks represented by letters, A
(adenine), T (thymine), G (guanine) and C (cytosine). The number
and order of these letters, also called bases, determine what we
are, how we look, and the diseases to which we may be
predisposed. The chromosome 22 te