Carrier testing

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Carrier testing is a type of genetic testing that is used to determine if a person is a carrier for a specific autosomal recessive diseases.[1] This kind of testing is used most often by couples who are considering becoming pregnant to determine the risks of their child inheriting one of these genetic disorders.[2]

Background[edit]

Genes come in pairs; one from the mother and one from the father. A carrier is a person who inherited one abnormal gene from one of their parents.[2] Carriers often show no symptoms of the genetic disorder that they carry an abnormal gene for. Usually the only time a person finds out that they are a carrier for a specific genetic disorder is when they have an affected child.[2] For these kinds of genetic diseases to be present in a person, two copies of the abnormal gene are needed. This means that both of the parents have to be a carrier for the child to inherit the disease.[1]

Reasons for Testing[edit]

The most common reason for carrier testing to allow future parents to find out if they are a carrier for a genetic disorder. If the parents are a carrier for a genetic disorder they can know ahead of time what their probability is of having an affected child. Carrier testing can be done before or during the pregnancy.[1] Many of these genetic disease are fatal at a young age which oftentimes encourages parents to get tested.[3]

Autosomal Recessive Disorders/Diseases[edit]

There are hundreds of recessive genetic disorders, most of which are very rare. Certain genetic disorders tend to be more common in people of a particular ethnicity.[4] For example, people of African American ethnicity have a much higher likelihood of being a carrier for the autosomal recessive disorder called sickle cell anemia.[3] People of one ethnicity in particular, Ashkenazi Jewish, have a tendency to be carriers for a wide variety of recessive genetic disorders. There are also several recessive disorders that are present in all ethnicities. This list includes: Cystic Fibrosis, Fragile X Syndrome, and spinal muscular atrophy.[3]

Testing Methods[edit]

Carrier testing is most often done through a simple blood test.[4] The results from these tests are usually available anywhere between two and eight weeks depending on where the testing is conducted.[5] There is another method of testing that is sometimes used. This type of testing analyzes gene products that are usually present in a person that keeps the genetic disorder from occurring. An affected person with the disorder would have close to a hundred percent reduction of the gene products compared to an unaffected person. A carrier would only have a fifty percent reduction in those gene products.[6]

Risks Involved[edit]

The physical risks for getting this kind of genetic testing done are very minimal. The most common requirement is a blood sample.[7] The emotional risks on the other hand are great. When a person finds out they are a carrier for a specific genetic disorder, dealing with that can be very difficult. In many cases, people who find out they are carries can become angered or even enraged that they carry a genetic defect that could be passed on to their child.[7] These results can play a role in determining if a couple will have a child together. If both parents are carriers for the same genetic disorder, there is a twenty-five percent chance that any child they have could be affected.[1] When a person finds out they are a carrier, they are always encouraged to talk to a genetic counselor.[5] If both partners are carriers for the same genetic disease, the choice to have a child together can become much more difficult.

References[edit]

  1. ^ a b c d "Genetic Screening Tests – Autosomal Recessive Diseases". OB/GYN Specialists of Palm Beaches, P.A. Retrieved 1 February 2014. 
  2. ^ a b c "Autosomal Recessive: Cystic Fibrosis, Sickle Cell Anemia, Tay-Sachs Disease". University of Rochester Medical Center. Retrieved 1 February 2014. 
  3. ^ a b c "Genetic Diseases". Genetic Disease Foundation. Retrieved 3 February 2014. 
  4. ^ a b "What is Carrier Screening?". GoodStart Genetics. Archived from the original on 19 January 2014. Retrieved 1 February 2014. 
  5. ^ a b Gilats, Michelle. "Carrier Screening Impact". Center for Jewish Genetics. Retrieved 2 February 2014. 
  6. ^ "About Carrier Testing". Department of Pediatrics: Clinical Genetic Services. Archived from the original on 6 March 2014. Retrieved 2 February 2014. 
  7. ^ a b "Pros and Cons of Expanded Carrier Screening". CEPMED. Retrieved 1 February 2014. [permanent dead link]