The first human genome was mapped in 2003 as part of the international Human Genome Project. It took 13 years and cost over USD 3 billion. Today it takes only a few days to sequence a genome and the cost is below USD 1000 with state-of-the-art equipment. Genomes are therefore sequenced as never before.
This technology is expected to improve the chances of diagnosing patients with a hereditary condition, and researchers are already taking advantage of its possibilities. Now that it is feasible to look through a patient’s entire genome, there is a greater likelihood of finding the cause of a genetic condition in more patients. At the same time, however, there is also a risk of finding other genetic mutations with little certainty about their potential impact.
From gene testing to genome testing
Within medical science it is only relatively recently that it has become possible to test genes in order to determine whether a person is at risk of a specific hereditary conditions. In 1983 the gene that causes the nervous system disorder Huntington’s chorea was found. This discovery enabled doctors to test people for specific genetic mutations causing the disorder. The first gene tests only considered individual genes, and testing was only carried out for a few conditions. These were diseases with simple correlations between a mutation in the individual gene and the condition (monogenic disorders).
Since the human genome was mapped, it has become clear that relatively few conditions are caused by mutations in individual genes, most conditions are much more complex. Researchers have also found out that the environment affects genes in ways we still have very limited knowledge about. The major public health conditions in the Western world, cardiovascular disease, diabetes, obesity and depression are likely caused by the interplay between several genes, and environmental factors, such as lifestyle.
Genetic testing cannot always locate a genetic mutation that causes disease. Even when there are clear indications that a family carries a hereditary condition, it may not be possible to locate the genetic cause, because all the mutations causing the condition may not be known.
Genome testing on the other hand enables searches for unknown variations, because the entire DNA is read, meaning that the base composition of all the the genes is mapped. Genome testing allows all the genes affecting the individual’s characteristics to be read, including any predisposition to a genetic condition.
Read about the benefits and risks of genome testing.
Read about genome testing and hereditary conditions.