Whose Genome is It, Anyway?
National Center for Human Genome Research, National Institutes
of Health. "New Tools for Tomorrow's Health Research." Bethesda, MD:
Department of Health and Human Services, 1992.
A quick glance around any public gathering will attest to the physical
diversity of the human population. In most groups of people, some
will be tall, others hefty; some will have brown eyes, and others
blue. Physical attributes such as height, complexion, and hair and
eye color are largely determined by genes - packets of the genetic
material DNA, which makes up chromosomes in the human cell.
As scientists begin to map and analyze the molecular details of the
complete set of human genes, whose will it be? In many ways,
describing the anatomy of the human genome will be similar to studying
the human heart, for example, or the human brain. While there are
small differences from person to person in the size and shape of these
organs, most of the key characteristics are the same. Although human
beings are distinct from one another, they are really very similar in
most biologically important respects. That's what makes us human. So
the map of the human genome can really be based on information
collected from many different people. And most of the information in
that map will pertain to everyone.
The tiny differences between any two people rest in only 2 to 10
million (out of the 3 billion total) nucleotide bases, an amount that
computes to about 1 percent or less of their total DNA. Because these
small differences vary from person to person, it doesn't matter whose
genome it is. For some studies, the differences will be the focus of
interest. In other cases, it will be the similarities. Researchers
at Baylor College of Medicine were given the assignment of mapping the
sex chromosome X and chromosome 17. They collected DNA from patients
who came into the clinic for genetic testing. Each sample is from a
different and unrelated person. The cell culture collection contains
a number of different human genomes.
Eventually, scientists will "map", or establish distinctive genetic
landmarks, from one end of a chromosome to the other and add that
information to the genetic map of the entire human genome. This
complete map will become the "reference" to which researchers will
compare DNA taken from a variety of people, as scientists look for
disease genes and other important genetic regions located on
chromosomes. A particular region on a chromosome, for example, may be
found to contain information about height. Although the genetic
content of that specific site may change slightly from person to
person, the location of the site will be the same in each person's
Because studying the entire six-foot stretch of human DNA is a huge
project, scientists are tackling the genome one chromosome at a time.
Even then, analyzing the information in just one chromosome is an
enormous task for a single research group, so many scientists are
studying only portions of a chromosome at a time. Even then,
analyzing the information in just one chromosome is an enormous task
for a single research group, so many scientists are studying only
portions of a chromosome. The complete map for a single chromosome
will then be derived from samples collected from several unrelated
people by researchers in many different laboratories.
For several decades, geneticists searching for disease genes have
studied human cells maintained in the laboratory. These cells
originally came from people who have an inherited disease, from their
healthy relatives who are carriers, or from other unrelated healthy
people. But because human cells do not ordinarily survive long under
laboratory conditions, scientists have had to invent ways to keep the
cells alive long enough to perform detailed studies of DNA inside the
Since almost all cells in the body contain the same genetic
information, nearly any type of cell can be used as a source of DNA.
A type of white blood cell called a lymphocyte is commonly used
because it is easy to obtain from a blood sample. To get the cells to
last longer in the laboratory, scientists infect lymphocytes in the
test tube with a common virus known as EBV. This virus, the cause of
mononucleosis, interrupts the cell's normal life cycle so it literally
doesn't know when to die. Cells "immortalized" by EBV then grow and
divide indefinitely in laboratory cultures, providing researchers with
unlimited amounts of human DNA for genome studies.
In most labs, the donors of these pieces of biology's greatest puzzle
will never be known. They are the genetic equivalent, according to
one researcher, of the unknown soldier.
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