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
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
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
(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
mail: ORNL Review
Oak Ridge National Laboratory
Oak Ridge, TN 378312-6144
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Date Posted: 1/10/94 (ktb)