Genetic Variation

Clinical Applications of Genomics : Genetic Variation

Completed in 2003, the Human Genome Project was a 13-year project coordinated by the U.S. Department of Energy and the National Institutes of Health. During the early years of the project, the Wellcome Trust (U.K.) became a major partner; additional contributions came from Japan, France, Germany, China, and others. Project goals were to: Identify all the approximately 20,000-25,000 genes in human DNA, Determine the sequences of the 3 billion chemical base pairs that make up human DNA, Store this information in databases, Improve tools for data analysis, Transfer related technologies to the private sector, and Address the ethical, legal, and social issues that may arise from the project. http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml

Each person, with the exception of identical (monozygotic) twins, has a unique genomic DNA sequence. Since each person has about 3 billion base pairs of genomic DNA and the base at each position could be one of four different bases, the total number of possible variations in genomic DNA sequence vastly outnumbers the human population.

Types of Genetic Variation

Terms used to indicate variations in DNA sequence include "mutations," "polymorphisms," or "alleles." Typically, mutations are relatively uncommon genetic variations that are known to be associated with a disease or an adverse health condition. Polymorphisms are common genetic variations that are not typically associated with disease. However, the association of a particular genetic variation with a disease is sometimes unclear, which can make it hard to distinguish a mutation from a polymorphism. An allele is another term for genetic variation and it could refer to either a polymorphism or a mutation.