Genetic testing is a powerful tool that can help us understand our health and the health of our families. It can be used to diagnose rare genetic disorders, identify hereditary mutations that can increase or decrease a person's risk of developing common diseases, and even predict the response to certain medications. In this article, we'll explore the different types of genetic testing, how they work, and what they can tell us about our health.For small DNA mutations, direct DNA testing may be the most effective method, especially if the function of the protein is unknown and a biochemical test cannot be developed. A DNA test can be performed on any tissue sample and requires very small amounts of sample.
Polymerase chain reaction (PCR) is a common technique for making numerous copies of short sections of DNA from a very small sample of genetic material. This process is called “DNA amplification” and makes it possible to detect or measure specific genes or regions of interest.This method is often used to copy DNA, so that it can be sequenced or analyzed with other techniques. It is often used to help search for genetic variants that are known to cause certain diseases, such as those associated with cancer or genetic disorders. For many years, Sanger sequencing has been the reference standard for clinical DNA sequencing to analyze individual genes or a few genes at a time.
It is based on a special chemical substance that marks each DNA nucleotide with a fluorescent dye of a different color, depending on the A, T, C or G base it has.This is the same technique that was used in the Human Genome Project. Sanger sequencing is reliable, but it can only read a short section of DNA from a patient at a time. Microarray testing is a technique used for a wide variety of purposes. In diagnostic tests, microarrays can be used to determine if a person's DNA contains a duplication, a deletion, or large extensions of identical DNA, which can sometimes cause disease.Like karyotyping, the microarray test looks at all the chromosomes at once, but it can detect smaller changes than those that can be detected by the karyotype or FISH.
Microarrays are made up of thousands of short, synthetic, single-stranded DNA sequences attached to a solid surface, such as a bead or a chip. DNA sequences comprise the normal gene being tested, as well as different versions of that gene that have been found in humans. The DNA from a person's sample is processed and labeled with a fluorescent dye and added to the microarray.The resulting fluorescence pattern is examined and interpreted. Specific points along each chromosome are examined to see if there is additional or missing chromosomal information.
For example, a duplication would indicate that there is one more copy of the chromosomal information than normal and a deletion is one copy less than normal. Microarrays can also include additional information collected from single nucleotide polymorphisms (SNPs).Although these SNPs don't actually provide us with sequencing information (that is,. They cannot determine which base (A, T, C or G) is present), they can identify which base pair is present (A&T or C&G) in a specific location. This additional information helps determine if there are regions on the chromosomes that appear identical (which is not typical, since one chromosome is inherited from the mother and another from the father).
If there is an autosomal recessive disease gene in this region and there is a variant that causes it, it will be present in both copies and, therefore, is expected to cause the autosomal disorder associated with that gene.Chromosomal microarrays are considered a first-level test for people with developmental delays, intellectual disabilities, autism spectrum disorders, or multiple birth defects, and are recommended instead of a karyotype. The gene expression profile analyzes which genes are turned on or off in cells. Gene expression is the process of producing specific proteins from information contained in genes. Different tissues express different sets of genes depending on their function in the body.The information from the gene is used to create a template for building the RNA.
The RNA then undergoes specific modifications to create the protein required by the cell. Gene expression tests evaluate the RNA in a person's tissue sample to determine which genes are actively producing proteins. For example, gene expression profiles are now available for breast cancer.These tests evaluate the products (RNA) of specific groups of genes in malignant breast tumors to predict the prognosis, recurrence and spread (metastasis) of the cancer, as well as to guide treatment. Its ultimate goal is to develop a personalized approach to patient care and breast cancer therapy.Genetic testing generally has little physical risk.
Blood and swab tests are almost risk-free. However, prenatal tests such as amniocentesis or chorionic villus sampling have a small risk of losing the pregnancy (miscarriage). Genetic tests have been developed for thousands of diseases. Most tests look at individual genes and are used to diagnose rare genetic disorders such as fragile X syndrome and Duchenne muscular dystrophy.In addition, some genetic tests test for rare hereditary mutations in genes that would otherwise be protective such as BRCA1 and BRCA2 which are responsible for some hereditary breast and ovarian cancers.
However more and more tests are being developed to analyze multiple genes that can increase or decrease a person's risk of suffering from common diseases such as cancer or diabetes.These tests and other applications of genomic technologies have the potential to help prevent common diseases and improve the health of individuals and populations. For example predictive genetic testing can be used to help determine the risk of developing common diseases and pharmacogenetic testing can be used to help identify genetic variations that may influence a person's response to medications. Much remains to be learned about the effectiveness of these new tests and how best to use them to improve health. Genetic testing can be done with small samples of blood or saliva (saliva).
In pregnant women genetic testing can....