CHAPTER 20: GENETIC TESTING, GENETIC COUNSELING, AND

GENE THERAPY

Abbey Deutschman Brittany Prentice

Colby Peters

Introduction

In the world of Genetic Testing and Treatment, Genetic Counselors play a key role in the discovery of specific disorders, the linking to support groups, and general help with genetic testing. If a specific disorder is treatable or not, it can be determined by genetic testing. Gene therapy also plays a role in the treatment of disorders or conditions in that both kinds of gene therapy, Germaline Gene Therapy and Somatic Gene Therapy, help treat disorders with an injection to the affected site or into a specific cell to regenerate.

20.1 Genetic Counseling

Because of predictable frequencies genetic diseases strike families in a way that other conditions do not. Professional genetic counselors help individuals and families identify genetic diseases and overall help the people.They trace back through family history genetic diseases and embrace multi-factorial disorders like cancer.Lots of times a genetic counselor will explain Mendel’s Laws, but substitute the particular family’s situation instead of the pea experiments.

Genetic Counseling Continued

A typical genetic counseling session involves family history, pedigree construction, information on specific disorders, testing, links to support groups and a follow-up contact.Reasons to seek genetic counseling are: a family history of abnormal chromosomes, multi-factorial disorder, and/or cancer.The steps taken towards living with genetic diseases are realizing something is wrong, diagnosing the condition, identifying a mutation in others and treating symptoms.Genetic counselors that find genetic problems can conclude that 1 in every 4 children the parents give birth to will have a genetic disease.

20.2 Genetic Testing

Newborn Screening is a routine screening that helps to detect disorders early and allows for treatment in some disorders, over 50 disorders can be detected.Using Tandem Mass Spectrometry inborn errors of metabolism can be identified.Testing for inborn errors of metabolism is not costly because there is only one blood sample needed and it is done anyway.Genetic testing has many uses and not just on newborns.

More Genetic TestingTypes of Genetic Tests

Type of Test

Information Obtained

Carrier Screen Identifies heterozygotes

Prenatal Tests Detects mutant genes for a condition in the family

Prenatal Screen Tests embryos for an increased risk of a condition, not based on family history

Newborn Screen Testing for several treatable inborn errors of metabolism

Diagnostic Test Confirms diagnosis based on symptoms

Predisposition Test

Detects alleles associated with an illness

Predictive Test Detects mutation in an individual at high risk based on family history

Problems with Genetic Testing

Issues are raised with genetic testing here are a few:

Privacy issues and confidentiality about test resultsEconomic issuesEthics

20.3 Treating Genetic Disease

Gene Therapy2 ways healing genes are administered :

Germline Gene Therapy- Changes the DNA of a gamete or fertilized ovum. All the cells of that person will undergo the correction and is passed to offspring. Is currently not being done on humans.Somatic Gene Therapy- Changes only the cells directly affected by a disease or illness. Is not passed to offspring. There are 3 options:

Genes can be removed from body, changed and then infused back into the body, called ex vivo therapy. In Situ therapy is when genes plus DNA are injected into a localized area, such as a single cell of a melanoma.When the vector is introduced straight into the body, that is called In vivo therapy.

Gene Delivery

There are 3 ways to send DNA into cells:Physical- which includes electroporation, microinjection, and particle bombardment. Chemical- which lipids that carry DNA across the plasma membrane, such as liposomes.Biological- uses a vector such a as a viral genome that has had the gene that causes illness removed and replaced with the healing gene.

Sites of Gene Therapy

Genes can be injected into the tissue that is being affected or it can be injected into specific cells that can regenerate the needed protein and divide. Site of delivery that are currently being trialed via stem cells and progenitor cells include:

EndotheliumSkinMuscleLiverLungsNervous SystemCancer

Conclusion

In conclusion, Genetic Counselors can be used to find information on specific disorders, help with genetic testing, and offer links to support groups. Genetic testing can be used to find specific disorders and determine if they are treatable. There are two types of gene therapy in which to treat disorders: Germline Gene Therapy and Somatic Gene Therapy, which can be injected into the affected site or into a specific cell to regenerate.

Bibliography

[2, 3] Human Genetics. (2008). Ricki Lewis. Retrieved July 1, 2009. P. 394-396Gene Therapy. Human Genome Project, Genomics.energy.gov