Download how is deafness inherited?

Human Heredity
November 2010
Erin Stafford
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Introduction:
What is Hereditary Deafness?
Hereditary deafness is hearing loss that is passed down
from parents to their children. Nonsyndromic hereditary
deafness is hearing loss with no other medical conditions
present other than deafness.
I am interested in this topic because I know people that
have nonsyndromic hereditary deafness that have
hearing parents and hearing siblings. In researching the
question, How is Deafness Inherited? I would like to find
out why only some people in a family inherit deafness.
http://findarticles.com/p/articles/mi_m0DVD/is_1992_August/ai_15097323/
http://hearing.harvard.edu/info/genetics.pdf
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How is Nonsyndromic Deafness
Inherited?
 Most hereditary hearing loss is nonsyndromic.
 80% of nonsyndromic hereditary hearing disorders are
autosomal recessive.
 Autosomal recessive means that both parents must be
carriers of the same gene mutation in order for a child to
inherit the disorder.
 When both parents are carriers of the recessive gene
mutation, there is a 25% chance that their child will inherit
the disorder.
http://www.dhss.mo.gov/Genetics/TalkCornerArchives/6_06NewbornHearingLoss.html
Cummings, M. and Yashon, R. Human Genetics and Society.
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Inheritance Pattern
for Autosomal
Recessive Gene
Mutation
Diagram: U.S. National Library of
Medicine
State of Missouri Dept.of Health
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What Causes Nonsyndromic
Hereditary Deafness?
The genetic cause of
hereditary deafness is
from a mutation in the
gene that makes a
protein called Connexin
26.
This is a sensorineural
deafness or nerve
deafness. The cochlea
cannot change sound
waves into a signal that
can be sent to the brain.
Colorado Neurological Inst.
Diagram: Harvard Medical School
Pamphlet: Hereditary Deafness
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Genetic Link
The genetic cause of
nonsyndromic hereditary
deafness is from mutations in
the gene that makes
Connexin 26, a protein.
The gene that codes for
Connexin 26 is called Gap
Junction Beta 2 (GJB2).
This gene is located on
the long arm of
chromosome 13.
Diagram: National Library of Medicine, Genetics Home Reference
Genetics: JGB2
National Library of Medicine Genetics Home Reference Genetics
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Gap Junction Beta 2 (GJB2)
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•
•
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People whose deafness is related to
Connexin 26 have a variant of the GJB2
gene that does not make the protein
Connexin 26 .
The protein Connexin 26 is present in
the cochlea and outer skin cells.
Connexin 26 helps in the formation of
small channels called gap junctions
between cells in the cochlea.
These gap junctions serve as a way for
the recycling of small potassium
molecules, which are necessary for
hearing.
Without Connexin 26 protein, gap
junctions do not form correctly, so
potassium cannot be recycled in the
cochlea.
UCLA Deaf Genetics Project
Diagram: University of Michigan
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Genetic Testing
Is Genetic testing for
hereditary deafness
available?
 Genetic testing for
connexin 26 is available
to children who are born
deaf.
Deafness and Hereditary Hearing Loss Overview
Harvard Medical School Center for Hereditary Deafness
How can genetic
information help?
• Genetic testing allows an
understanding of the
hearing loss and what
type of damage there is
in the hearing system.
• Provides improved
treatment choices.
• Can help in reproductive
choices.
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A Note About Genetic Testing
It can be extremely
disturbing for a parent to
find that because of a
gene mutation they carry
their child is deaf. It is
important to remember
that gene mutations are
common, and that no
one is responsible for the
genes they carry.
Artwork : Concurring Opinions
Harvard Medical School Center for Hereditary Deafness
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Works Cited
Barlow-Stewart, Kristine and Saleh, Mona. The Australasian Genetic
Resource Book. Center for Genetics Education. June 2007. Web. 26 October 2010.
<www.genetics.edu.au>.
Berke, Jamie. Cause of Hearing Loss-Genetics. About.com 19 March, 2009. Web. 26 October
2010.<http://deafness.about.com/od/medicalcauses/a/genetics.htm>.
Cincinnati Children’s Hospital and Medical Center. Genetic Testing for Hearing Loss. Web. 26 October 2010.
<www.cincinnatichildren.org>.
Colorado Neurological Institute. Therapy. Web. 26 October 2010. <www.thecni.org>.
Deaf Genetics Project. University of California, LA. Web. 20 October 2010. <http:deafgeneticsproject.org>
<http://www/geneticalliance.org.uk/docs/translations/english/35-deafness-t.pdf>.
“Genetic Deafness”. Genetic Alliance UK. July 2005. Web. 26 October 2010. <www.geneticalliance.org>.
Hegarty, Joseph L.Genetic Causes of Sensorineural Hearing Loss.
Spring, 2005. CNI. Web. 26 October 2010.
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Works Cited
Moody, Stephanie A. and Strasnick, Barry.
“Inner Ear, Genetic Sensorineural Hearing Loss”.
Emedicine. June 2009. Web. 26 October 2010
<http://emedicine.medscape.com/article/855875>.
“ Nonsyndromic Deafness”. Genetics Home Reference. U.S. National Library of Medicine. 24 October 2010. Web.
26 October, 2010.
<http://ghr.nlm.nih.gov/condition/nonsyndromic-deafness>.
Rehm, Heidi, et al. Understanding the Genetics of Deafness. Harvard Medical School Center for Hereditary
Deafness. Web. 26 October 2010. <http: hearing.harvard.edu>
Smith, Richard JH and VanCamp, Guy. Deafness and Hereditary Hearing Loss.
January 2007.University of Washington, Seattle. Web. 26 October 2010
<www.geneclinics.org/profiles/deafness-overview/details.html>.
University of Michigan Health System. “Gene Mutation That Causes Rare Form of Deafness Identified.” Science
Daily 13 July 2010. Web. 26 October 2010 <http://www.sciencedaily.com/releases/2010/100702154527.htm>.
Yukon, Ronnee and Cummings, Michael. Human Genetics and Society. California: Cengage Learning, 2009
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Works Cited
Photos, Diagrams and Artwork
Slide 1: Photo: Family, meredithsmall.wordpress.com
Slide 4: Diagram: Autosomal Recessive, U.S. National Library of Medicine. www.dhss.mo.gov
Slide 5: Diagram: Ear, Harvard Medical School Center for Hereditary Hearing Loss
Slide 6: Diagram: Chromosome 13, National Library of Medicine, Genetics Home Reference: Genetics: GJB2
Slide 7: Artwork: Gap Junction Beta 2, University of Michigan
Slide 9: Artwork: Genetic Testing, Concurring opinions. www.concurringopinions,com
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