Most of any one person’s DNA, about 99.9 percent, is exactly the same as any unrelated person’s DNA. The human genome contains about 3 billion bases of DNA and almost every cell in the body contains a copy. Differences in the sequence of DNA among individuals are called genetic variation. Genetic variation explains some of the differences among people, such as eye color and blood type. Genetic variation also plays a role in whether a person has a higher or lower risk for getting particular diseases.
SNP Variation
The DNA instructions are passed with very great fidelity
from one generation to the next. However, occasionally a
mutation occurs and effectively changes one base to another.
The site of this base change is called a single nucleotide
polymorphism (or SNP). SNP variation occurs when a single
nucleotide, such as an A, replaces one of the other
three-nucleotide letters—C, G, or T.On average, SNPs occur
in the human population more than 1 percent of the time.
Because only about 3 to 5 percent of a person’s DNA sequence
codes for the production of proteins, most SNPs are found
outside of these protein coding regions. SNPs found within a
coding sequence are of particular interest as they are more
likely to alter the biological function of a protein.
Although many SNPs do not produce detectable changes in
protein function, other SNPs may predispose people to
disease and influence their response to drug regimens.
SNPs & Disease
Many common diseases in humans are not caused by a genetic
variation within a single gene but are influenced by complex
interactions among multiple genes as well as environmental
and lifestyle factors. Although both environmental and
lifestyle factors add tremendously to the uncertainty of
developing a disease, it is currently difficult to measure
and evaluate their overall effect on a disease process.
Therefore, it more accurate to think about SNPs in how they
influence a person’s genetic predisposition, or the
potential of an individual to develop a disease based on
genes and hereditary factors.
Genetic factors may also confer susceptibility or resistance to a disease and determine the severity or progression of disease. Because we do not yet know all of the factors involved in these intricate pathways, researchers have found it difficult to develop screening tests for most diseases and disorders. By studying stretches of DNA that have been found to harbor a SNP associated with a disease trait, researchers may begin to reveal relevant genes associated with a disease. Defining and understanding the role of genetic factors in disease will also allow researchers to better evaluate the role of non-genetic factors—such as behavior, diet, lifestyle, and physical activity
Functional Variation
Most SNPs in genes identified thus far have no functional
consequence, as they do not alter the structure of proteins
coded by that gene. In trying to associate SNPs with
health-related outcomes, it is more effective to focus on
that subset of SNPs that do cause a change in the
protein--this type of variation is called functional
variation. At VitaPath we focus our research primarily on
SNPs that cause functional changes as they represent the
most clinically relevant forms of genetic variation. In
order to assess the functional consequences of SNP
variations, our Technology Platform uses a yeast model
systems to obtain a direct, biochemical measurement of a
particular SNPs influence. Once functional SNPs have been
identified and characterized, we use this very selective set
to associate genetic variation with health and disease.
To read more about our functional SNP approach: http://www.pnas.org/content/105/23/8055.full.pdf
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