Several years ago, the human genome was decoded. This enormous project identified the general order, or sequence, of the building blocks of human DNA. Since that time, DNA scanning technology has significantly advanced our understanding of the relationship between genes and disease.
* What Is a Genome? *
A genome is the entire complement of genetic material (DNA) of an organism; in essence, it is the blueprint for making and operating a living thing. DNA is a type of nucleic acid; a huge organic molecule made of building blocks called nucleotides. A nucleotide monomer consists of 3 portions:
* a pentose sugar
* one or more phosphate groups
* one of five cyclic nitrogenous bases
The only thing that makes one nucleotide different from another, is the specific nitrogenous base that it contains; either cytosine (C) and guanine (G), adenine (A) or thymine (T). The human genome contains about 3 billion nucleotide base pairs.
It is the order of these bases that make living things different; different from other species and different from other members of the same species. The genomes of individual humans are more similar than, for example, the genome of a human compared to that of another species (ape, lizard, bacteria, plant-you get the picture).
Even though human genomes are similar to each other, no two humans, except for identical twins, have exactly the same DNA sequence. People typically differ in which base (C, G, A or T) they have at about 10 million positions along the entire genome. One person may have a G where someone else had a T.
* Human Genome & International HapMap Projects *
This revolution in genetic sequencing was made possible by the Human Genome Project in 2003 and the International HapMap Project in 2005. The purpose of these projects was to identify the order of the bases in the human genome.
Because of the advancements made during these genetic projects, researchers now have new data and technologies, including computerized databases that contain the reference human genome sequence as well as tools that can quickly analyze genome samples.
* Genome-wide Association Studies *
Many scientists and research groups are now carrying out genome-wide association studies, which involve rapidly scanning markers (DNA sequences used to identify a particular location on a chromosome) across the genomes of many people to find genetic variations associated with a particular disease.
Since 2005, studies employing this gene-scanning technique have discovered nearly 100 DNA variants to 40 common diseases and traits, including prostate cancer, heart disease, multiple sclerosis, gallstones and restless leg syndrome, to name just a few.
Being aware of genetic variants that increase the risk of certain diseases does not mean that we know how to cure or prevent these illnesses; at least not yet. But once genetic links are identified, researchers can use the information to develop better strategies to detect, treat and prevent the disease.
* More Information on the Human Genome *
To learn more about The Human Genome Project and Genome-wide Association Studies, see the NIH National Human Genome Research Institute website.
