Chromosomes in Nucleus 23 Pairs of Chromosomes MOM DAD
One Chromosome Pair Genes “instruction manual”
Chromosome Pair Genes Mutation “error”
How Is Mutation Inherited? Dominant ~15% Recessive ~80% X-Linked ~2% Mitochondrial >2%
Dominant Inheritance Mutation “error"
Carrier Mutation “error"
How a Recessive Mutation is Passed? Carrier –No Hearing Loss Affected Child— Hearing Loss
If a parent has a dominant mutation, EACH of their children has a 50% chance of having hearing loss Dominant Inheritance Recessive Inheritance 90% of all children w/HL have normal hearing parents! Parent w/HL Parent w/o HL Child w/HL If two parents have a recessive mutation, EACH of their children has a 25% chance of having hearing loss
HOW? WHO? WHY?
HOW Do We Know If HL is Genetic?
WHO Should Have a Genetic Test? Case A: Syphilis Case B: CMV Case C: Prematurity Case D: High bilirubin level Everybody with Sensorineural HL Also 2 Mutations in Cx26!!
WHY Should We Have a Genetic Test?? Benefits for Genetic Testing a definite cause family members realize that they are carriers & determine risk factors for future children helps to find appropriate treatment/ management
Limitations for Genetic Testing does not necessarily find the answer severity of HL may not be predicted a person may have mutations, but not have HL
Things to Consider Things to Consider 1. Talk to knowledgeable professional Primary Care/ Pediatrician ENT Audiologist Clinical Geneticist Clinical Geneticist Genetic Counselor Clinical Molecular Geneticist
Things to Consider 2. What tests are done? Cx26 Cx30 Mitochondrial Tests Pendred 3. Cost
UNDERSTANDING TEST RESULTS (example Cx26)
What Does the Result Mean? Two Mutations are Found No Mutations are Found Mutations w/Unknown Significance One Mutation is Found ?? ~10% ~70% ~18% ~1%
One Mutation Found Mutation unrelated to deafness Test did not find 2 nd mutation Dominant mutation There may be a mutation in another gene
Future in Genetics and HL More Genetic Tests GeneChip Technology
Research Studies Connexin 26 Study- individuals with Cx26 mutations Genetic Testing and Counseling Study - If you or your child has had genetic testing for hearing loss and you are willing to fill out a questionnaire GeneChip Study - individuals with hearing loss who and parents with normal hearing Novel Gene Discovery Study - five or more family members with hearing loss
Now also in Spanish! Educational Material
Helpful Information Genetic Counselor - Rebecca Madore call to set an appointment or Department of Clinical Genetics – To make appointment with Clinical Geneticist call National Society of Genetic Counselors (NSGC) Research Study Participation & Booklets Orders: Anna Frangulov or or