Stephanie Belanger January 12, 2009 AP Bio

What is Tay-Sachs Disease? An inherited autosomal recessive condition that causes progressive degeneration of the central nervous system cessive.svg/300px-Autorecessive.svg.png

Common Names B Variant GM2 Gangliosidosis GM2 Gangliosidosis, Type 1 Hex A Deficiency Hexosaminidase A Deficiency Sphingolipiosis TSD view01_light_USF_phobic.png

History In 1881, Warren Tay, British ophthalmologist, discovered a cherry red spot on the retina of an infant Several years later Bernard Sachs, a New York neurologist, provided the first description of cellular changes in Tay-Sachs disease %20Common%20Eye%20Disorders/Retina/Retina%20jpgs/crao%20cherry.jpg

Mode of Inheritance Autosomal Recessive Gene Both parents are carriers, child inherits both recessive genes Caused by a mutation of the Hex A gene on chromosome 15 A55/0000BDF C68C /file/bb_feb2007_large.jpg

Tay-Sachs Description Deafness Decreased Eye Contact Blindness Decreased Muscle Tone Delayed Mental and Social Skills Dementia Increased Startle Reaction Irritability Loss of Motor Skills Paralysis or loss of motor function Seizures Slow Growth

Description Continued Without the enzyme Hex A, GM2 begins to strangle the nerves in the brain and begins to kill off nerve cells Children usually die by age 5, but some live longer Most commonly inherited in Ashkenazi Jewish and French Canadian cultures 1 in every 250 contract Tay-Sachs disease in the general population

Treatment No cure or treatment Suggested enzyme replacement therapy Substrate reduction drug Stem cell transplantation images/stem_cell1.jpg

Detection Cannot be detected before symptoms appear Disorder tested for once parents notice considerable changes in child’s development and motor skills Small percentage detected prenatal, but has been found through chronic villus sampling (CVS)

Ethical Issues “What is normal and what is a disability or disorder, and who decides?” “Are disabilities diseases? Do they need to be cured or prevented?” “Does searching for a cure demean the lives of individuals presently affected by disabilities?” “In somatic gene therapy (which is done in the adult cells of persons known to have the disease) more or less ethical then germline gene therapy (which is done in egg and sperm cells and prevents the trait from going on to other generations?” “Preliminary attempts at gene therapy are exorbitantly expensive. Who will have access to these therapies? Who will pay for their use?”

Legal Issues Human Experimentation Standard of Care Parental Authority Unfairness Negligence