Genetic Disease (cont.)

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What is the human genome?

The human genome is the entire "treasury of human inheritance." The sequence of the human genome obtained by the Human Genome Project, completed in April 2003, provides the first holistic view of our genetic heritage. The 46 human chromosomes (22 pairs of autosomal chromosomes and 2 sex chromosomes) between them house almost 3 billion base pairs of DNA that contains about 20,500 protein-coding genes. The coding regions make up less than 5% of the genome (the function of all the remaining DNA is not clear) and some chromosomes have a higher density of genes than others.

Most genetic diseases are the direct result of a mutation in one gene. However, one of the most difficult problems ahead is to further elucidate how genes contribute to diseases that have a complex pattern of inheritance, such as in the cases of diabetes, asthma, cancer, and mental illness. In all these cases, no one gene has the yes/no power to say whether a person will develop the disease or not. It is likely that more than one mutation is required before the disease is manifest, and a number of genes may each make a subtle contribution to a person's susceptibility to a disease; genes may also affect how a person reacts to environmental factors.

Medically reviewed by Edward Spence, MD; Board Certified Clinical Genetics with subspecialties in Clinical Molecular Genetics and Clinical Biomechanical Genetics/Pediatrics

REFERENCE:

National Human Genome Research Institute.
<http://www.genome.gov>

Previous contributing authors and editors: Barbara K. Hecht, Ph.D. and Frederick Hecht, M.D.


Medically Reviewed by a Doctor on 1/15/2014

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