punnet.pngHuntington’s Disease

Huntington’s disease (HD) affects the brain and the ability to think, talk, and/or move. HD destroys cells in the basal ganglia, which is the part of the brain that controls movement, emotion, and cognitive ability. This disease is caused by a genetic mutation in chromosome 4. People who have Huntington’s have abnormally high CAG triplets, approximately 40 or more while the normal person has 10 to 26. Brain cells accumulate clumps of protein that become toxic, resulting in cell death. Some patients lose 25% of their brain cells before they die.
HD is autosomal dominant, so one parent has the bad gene and the other parent is healthy. Everyone who inherits the faulty gene will eventually get the disease. A parent with HD has a 50% chance to pass on the disease to their child. The chromosome 4 has a defect, but gets passed on to the child. Children inherit an expanded Huntington gene from one parent. Nearly all people who have HD inherent it from one of their parents. Some cases neither biological parent has Huntington’s disease. This happens when the father has no Huntington gene with an intermediate number of CAG repeats from 27-35. The number of CAG repeat does not cause the father to get Huntington’s. His gene can gain more repeats in sperm he produces, that many repeats causes the child to get Huntington’s even though the father does not have HD.
Huntington’s disease affects the brain where it controls thinking, emotion, and movement. Patients usually start seeing symptoms when they are ages through 30-50, but can happen during anytime in their lives. HD does not get better but gets worse over time. Patients have poor memory, depression or mood swings, lack of coordination, and twitching or uncontrollable movements. Other Huntington’s disease effects are difficulty walking, speaking and/or swallowing. In later stages, patients need help doing the simplest of tasks.
Daily Life:

During pregnancy they can check to see if the child has HD two ways. Doctors can take fluid from around the fetus or take fetal cells from the placenta. After the child is born they can diagnose by doing a series of neurological and physiological tests. A genetic test can then confirm the diagnosis by determining if the person indeed inherited HD. Tests cannot show when the symptoms of HD will act up. Presymetomatic genetic testing is for individuals not showing signs of HD and involves genetic counseling. A testing program should include intial telephone contacts pre-screening interviews, three pre-test in-person sessions for genetic counseling, neurological evaluation and physiological evaluation, fourth session for disclosure of results and post test counseling. There are requirements for the diagnosis such as medical history, family history, and neurological examination, brain imagining tests, lab tests, and genetic history if necessary.
There is no cure for Huntington’s disease. There are medications that ease depression and anxiety, control involuntary movements. Physical or speech therapy helps patients lead more normal lives. Medications don’t slow the progression or reverse, but make them more comfortable. In August 2008 the U.S Food and Drug Administration approved tetrabenazine to treat involuntary movements, making it the first drug in the United States to treat the disease. It is extremely important for patients to maintain physical fitness. Researchers have found those who exercise and keep active tend to do better then those who don’t. Some of the medications they take are antipsychotics, antidepressants, tranquilizers, mood stabilizers, and botulinum toxin coystonia for jaw clenching. They have to intake enough calories for an adequate body weight. The food can be cut into small pieces to help them chew and swallow. Patients need large quantities of fluid.
Their have been investigations using electronic and other technologies enable scientists to see what the defective gene does to the brain and how it affects the body’s chemistry and metabolism. Lab animals are being bred to try duplicating the features of Huntington’s disease, so they can learn more about the symptoms and progression. Drugs are being studied to slow the progression of HD, but nothing has worked so far. Clinical trials are playing a key role in testing new treatments. Biomedical research on disorders of the brain and nervous system are being done. Investigators in the field of neurobiology, which encompasses the anatomy, physiology, and biochemistry, are working to find better treatments to help them live their lives normally. Imaging, animal models, and fetal tissue research are being done to try and see what can be done with Huntington’s.
Additional Facts:
This disease was named after Dr. George Huntington who first diagnosed it in 1872. 1 in every 30,000 people have HD, more than a quarter million Americans have Huntington’s. All ethnic groups are equally affected. Children who develop symptoms rarely live to adult hood. The symptoms can vary from person to person. Patients with Huntington’s disease can die from complications such as choking, infection, or heart failure. The person with HD isn’t the only one affected: the whole family gets affected emotionally, socially, and economically from having to care for the family member who has HD. Some patients stop recognizing family members or close friends.
Punnett Square:

Pedigree Chart:
Include hyperlink to websites that you used as part of your research.http://learn.genetics.utah.edu/content/disorder/whataregd/hunt/index.html http://www.ninds.nih.gov/disorders/huntington/huntington.htm