Pharmacogenomic: Some genes are responsible for how the body processes medications. Pharmacogenomic testing looks for changes in those genes and seeks to correlate that information to a person’s response to medications. It seeks to predict the most effective drug at the right dose, as well as identify those drugs that may cause harmful side effects. For example, warfarin is a drug that helps prevent blood clots, strokes and heart attacks. Individuals who have specific genetic variants require lower doses for therapy. Similar variants are associated with medications for depression and chemotherapy. While these types of tests are currently used for only a few health issues, they will become increasingly important in the years ahead. At the moment, no single pharmacogenomics test can predict an individual’s response to all medications. In addition, no such tests are available for most over the counter medications.
How does a human genome get sequenced?
Your genome is your unique sequence of DNA, 3 billion letters long. It’s found in almost every cell in your body. DNA
A denine T hymine C ytosine G uanine
Bases
Sugar phosphate backbone
The letters A , T , C and G represent the chemical elements, or bases, of DNA.
Ancestry:
a sequencing machine . 1
DNA is extracted from a sample and loaded on to
Because certain patterns of DNA variation are more commonly found among individuals of specific backgrounds, DNA analysis can shed light on where an individual’s ancestors likely came from. The more of these patterns that two people share, the more closely related they are. Genetic ancestry testing usually examines DNA variation on the Y chromosome (to study the male line), the mitochondria (for details about the female line) or single letter changes throughout the genome (to estimate the overall ethnic background). This type
2 The machine determines the sequence of short pieces of DNA,150 letters long. These are called reads . 3 The ‘reads’ from the sequencing machine are matched to a reference sequence. This is called mapping .
of testing does not reveal any medical or health-related information and while it may provide geographic origins for distant ancestors, it cannot provide the names of those ancestors.
Cancer:
Genetic testing may be useful as a predictive test for individuals with a family history of certain types of cancers (such as breast, ovarian and colorectal). A positive test result indicates the person has inherited a genetic mutation that significantly increases his or her lifetime risk of developing cancer. These individuals may have more frequent cancer screenings or chose to undergo surgery to reduce the cancer risk. In some cases, this type of genetic testing for inherited mutations may also be appropriate when cancer has already been detected. In addition, genetic testing of the tumor cells may be requested to determine which cancer-causing mutations have been acquired by the tumor. This knowledge may aid in diagnosis and shape a physician’s choice of therapy to treat the cancer.
4 Analysis
Within the 3 billion letters in your genome are 20,000 genes. These make up about 2% of the sequence. The position of most of our genes is known, and is marked on the reference sequence . Every person has millions of differences (called variants ) from the reference sequence. Most of these difference are harmless – they are the reason we are different from each other. Some differences could be causing a disease. Bioinformatics specialists use a variety of tools and techniques to filter these differences down from millions to just a handful that could be harmful. If it is not clear which difference is causing disease, researchers anaylze the genome further.
Identity Testing: DNA profiling identifies an individual’s unique pattern of DNA variation and is often used in parentage testing and criminal investigations.
A parent shares 50% of his or her genetic variation with a child. A paternity or maternity test compares the DNA patterns between the child and alleged parents to look for evidence of genetic sharing. Forensic DNA testing can link a perpetrator or victim to a crime scene as well as exonerate individuals convicted of crimes they did not commit. There are limitations to this type of testing, including the
inability to distinguish between identical twins and the challenge of assessing samples with degraded or low amounts of DNA.
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SCIENCE FOR LIFE
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