ORNL PROBES THE HUMAN GENOME 
   
   
   Research into the human genome at ORNL is focused on genome mapping and
   DNA sequencing. The genome is subdivided into chromosomes, each of which
   contains thousands of genes. Determining the order of these genes and
   the spacing between them is called mapping. Understanding a gene's
   function involves unraveling the codes it contains for specifying
   protein structure and for turning the gene on and off. The codes are
   specific sequences of nucleic acid bases, so determining the order of
   these bases is the goal of DNA sequencing.                 
   
   This delving into human genetic roots has yielded information on
   thousands of genes, including those responsible for such disorders as
   muscular dystrophy, cystic fibrosis, and Huntington's disease.
   Researchers are hopeful that, as they uncover the causes of genetic
   diseases, they will also be able to develop genetic "fixes" for these
   conditions.         
   
   An individual's genetic information is normally recorded on 46
   chromosomes (23 from Mom and 23 from Dad). These chromosomes comprise
   roughly three billion pairs of bases, throughout which are scattered the
   estimated 50,000 to 100,000 genes of the human genome.
   
   Despite these daunting numbers, there are only four kinds of DNA
   bases--adenine (A), thymine (T), cytosine (C), and guanine (G). These
   bases are arranged in sets of three (for instance, AAA, CGC, or GAC),
   called codons. Different groupings of codons correspond to the various
   amino acids or regulatory signals to the cell. Genes, then, are strings
   of amino acids that build proteins and regulate cell function.             
         
   
   For practical purposes, think of the DNA molecule as a ladder with a
   strand of phosphate and sugar molecules on each side and pairs of bases
   between the strands for rungs. Because DNA bases come in matched pairs
   (A bonds with T, and C bonds with G), knowing the sequence of the bases
   on one side of the ladder makes it possible to determine the sequence
   the other.          
   
   ORNL researchers have adopted a number of approaches to sequencing and
   mapping DNA. Some methods are the highly efficient descendants of
   techniques that have been used for years, such as gel electrophoresis
   and radiolabeling; others employ nontraditional technologies, such as
   laser ionization and computer modeling.             
   
   The result is a wide array of research programs that spans several
   research disciplines. Many of these programs are described in the 
   following articles.
      
   
   (keywords: genetics, Human Genome Project, DNA sequencing)
   
   These articles also appear in the Oak Ridge National Laboratory Review
   (Vol. 25, No. 1), a quarterly research and development magazine. If
   you'd like more information about the research discussed in the articles
   or about the Review, or if you have any helpful comments, drop us a line
   at: 
   
        email 
   
        fax:             615/574-1001 
   
        phone:           615/574-7183 
   
        mail:            ORNL Review 
                         Oak Ridge National Laboratory
                         4500-S 6144 
                         Oak Ridge, TN 378312-6144
   
   Thanks for reading the Review.
   

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   Date Posted:  1/10/94  (ktb)