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	Presentations on Genetic Screening 3/19/03 Diagnosis and Treatment using Genetic Screening Karen   Methods for Diagnosis Biochemical Test for enzyme or metabolic byproduct (or the lack of) Gross Chromosome Analysis /Karyotyping DNA Sequence Analysis DNA Mutation Screening   Genetic Screening- Benefits to Individual: Treatment or ability to plan based on genetic status Tay-Sachs - avoidance of birth of children with genetic phenotype. Phenylketonuria - immediate treatment of children born without enzyme to eliminate condition. BRCA1 - Enhanced motivation to reduce other cancer inducing environmental influences. Pharmacological choices determined by genetic profile. Tissue and Organ Transplantation more accurate matches. Genetic Therapy to alter known condition.   Factors that influence ability to Diagnose and Treat based on Genetic Tests Accuracy of test Recessive vs Dominant Point mutation of single gene or interaction among multiple gene alleles Penetrance Treatments available   Overview of Genetic Testing: Penetrance in suceptibility to cancer When a genetic disease is the result of a interaction among genes, often the first mutation is not enough to cause the disease but makes the cell vulnerable if an environmentally induced mutation occurs. The cell may be able to repair DNA damage resulting from an original mutation until the repair mechanisms are also damaged or the cell is otherwise overwhelmed. It make take multiple mutations to fully activate a malignancy.   Complexity of BRCA1, BRCA2, Fanconi Interaction Source: http://www.biocarta.com/pathfiles/h_atrbrcaPathway.asp#history General Description of BRCA/Fanconi Interaction: When a cell's DNA is damaged - whether by excessive sunlight, chemicals such as those found in cigarette smoke, radiation, or other means - five of the Fanconi genes team up to produce a protein "complex" that stimulates a sixth gene. That gene, dubbed D2, orders production of a protein that moves near BRCA1, whose job is to help repair damaged DNA. If BRCA1 or its partner in DNA repair, BRCA2, are defective or aren't switched on properly, DNA damage can accumulate in cells, increasing their chances of malfunctioning and becoming cancerous. This complexity of interaction, as well as hundreds of variations of the BRCA1 gene, make the diagnosis and prognosis for carriers of BRCA1 uncertain at the current time . This complexity explains the penetrance of BRCA1 being only 60-85%.   Issues with Genetic Screening for Diagnosis and Treatment: 1. Informed Decision Making. Adequate counseling before testing, to interpret test results and choose options for treatment or other actions. 2. Privacy and Confidentiality. Discrimination by employer or insurance or family/friends. 3. Freedom of Choice. Pressures to be tested, know results and make reproduction choices, by individual and family members. 4. Health Care Costs. Cost of testing and treatment, but also cost of NOT testing if the public is funding health care costs.   Case Examples: Would you take the genetic test and what would you do with the results? Phenylketonuria Tay-Sachs BRCA1 Huntington's Chorea   References: U.S. Department of Human and Health Services, Access Excellance Research Center, "Understanding Gene Testing", http://www.accessexcellence.org/AE/AEPC/NIH/ Nuffield Council on Bioethics 2001, "Genetic Testing", http://www.nuffieldbioethics.org/publications/geneticscreening/rep0000000062.asp GeneReviews, BRCA1 and BRCA2 Hereditary Breast/Ovarian Cancer, http://www.geneclinics.org/profiles/brca1/index.html, last update 3/4/2000 Cancer Genetics Web, http://www.cancerindex.org/geneweb/BRCA1.htm  ..
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 Updated 3/25/03 by thatcher@sonoma.edu