Most people are aware of the fact that we all have genetic material that is used to construct a human. However, using the phrase “genetic testing” encompasses a number of different tests. A gene is a long string of chemicals that direct the construction of proteins. The body used proteins to function. So, if there is an error in the gene, the body may not function correctly.
Genes are organized in very long chains that shrink forming a sausage like structure called a chromosome. There are 23 different chromosomes. Humans get one copy of their genetic code from each parent, so humans have 23 sets of chromosomes with two chromosomes in each set.
Genetic testing can be done for humans from the embryo stage to the adult human. Adults may have a genetic test called a karyotype which counts the number chromosomes and determines if there are very large rearrangements.
Another type of genetic test determines if a gene is normal or abnormal (gene mutation). Gene mutations may cause very severe and debilitating diseases such as Cystic Fibrosis or Tay-Sachs disease. Remembering that there are two sets of genes, some disease will occur if the mutation occurs on just one set of genes. However, for many gene diseases, both genes need to be mutated. This causes a recessive genetic disease and the person with a single gene mutation is called a carrier.
People considering becoming pregnant can do prenatal genetic carrier screening where their genetic material can be tested to determine if they are carriers. Hundreds of possible deleterious gene mutations have been identified. If both the male and the female have a gene that has the same mutation, then one of four of the offspring will have the disease. Knowing this can help the people decide if they should test their embryos to see if the embryo has the disease.
Testing an embryo for a gene disease as another type of genetic testing which is done on embryos prior to their transfer. A common cause of miscarriage is pregnancies that have the wrong number of chromosomes. Pre-implantation embryos can be tested for chromosome numbers which is called karyotyping. Pregnant women can have their child tested while they are still pregnant. This has been done on amniotic fluid, placental cells from first trimester pregnancies, or from maternal blood. Lastly, miscarriages or stillborn children can be tested for genetic diseases especially karyotyping.