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The Human Genome Project has the potential to increase our knowledge of
disease and the diseases related to aging in ways unimagined by scientists
just a generation ago. The complete sequencing of the genome will ultimately
identify all genes associated with disease. Thus far, researchers have
identified about 1,000 genes associated with specific diseases. We are
now beginning to identify the associations between those genes, the proteins
for which they code, and certain disease features, such as the age of
onset and just how the disease is inherited.
The technology by which these genes are studied is a new and exciting
field called experimental genomics. This field employs a number of techniques
including gene expression array analysis, which looks at what DNA is actively
transcribed into RNA, the first step in the making of proteins. Other
newly developed and emerging laboratory techniques include genomic hybridization,
representational difference analysis, restriction landmark genome scanning,
and chromosome painting (for a relatively technical description of these
strategies, please click here
In short, these techniques allow scientists to understand what genes are
involved in specific bodily or disease processes, but their use in studying
something as complex as aging, with the multitude of genes in play, is
still limited.
Sophisticated gene analyses are helping scientists understand the role
of genes in certain cancers. Many cancers are associated with aging. They
occur with greater frequency among older adults than in other age groups.
Each time a cell divides, it must first duplicate its DNA, so that each
daughter cell receives a full complement of genetic material. Each time
DNA is reproduced, there is potential for error or mutation. Insertion
of the wrong base pairs into newly created DNA can remove some of the
normal controls over cell division, and allow cells to reproduce without
check; in other words, to become cancerous. Certain genes, called oncogenes,
are more prone to such mutations and cause very specific cancers. Analysis
of the genome suggests that the number of oncogenes we carry may be far
more than presumed. An understanding of what genes are involved in the
genesis of cancer is an important first step in controlling the expression
of those genes, and stopping cancer before it can start.
A number of other age-associated diseases are known to have some of their
roots in our genes. These include Alzheimer's disease, macular degeneration,
type 2 diabetes, and heart disease (although external forces, particularly
smoking, diet, exercise, etc. clearly contribute to a greater or lesser
extent, in each of these conditions). The unraveling of the genetic code
is allowing a greater understanding of the role our genes play in disease.
While the ethical implications of genetic testing are still being debated,
the knowledge that we carry genes that predispose to certain diseases may
permit us to make changes in diet, physical activity level and other areas
to defer and perhaps prevent the onset of those diseases.
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