Huntington's Disease Essay Example | Topics and Well Written Essays - 1250 words

Huntington's Disease - Essay Example This disease can develop at any age, however, it is most common between the ages of 30 to 50. HD was previously known as Huntington’s chorea. Chorea means jerky, involuntary movements. This paper provides a description of Huntington’s disease including its causes, symptoms, and treatment. Causes HD is caused by a genetic defect on chromosome 4. This disease causes part of DNA, known as a CAG repeat, to replicate itself more than it is supposed to (Lawrence, 2009). In normal conditions, this part of DNA section is repeated 10 to 28 times. However, in HD patients, it is repeated 36 to 120 times. Since this is a hereditary disease, the number of repeats tends to get bigger down the subsequent generations. Therefore, children having a larger number of repeats tend to develop symptoms of this disease at early ages. This condition affects basal ganglia that control balance and movement in human beings (WebMD, 2011). In the region of basal ganglia, HD mainly targets neurons of the striatum, especially those in the pallidum and caudate nuclei. There are two types of Huntington’s disease: adult-onset Huntington’s disease, which is the most common, and an early-onset form, which begins in childhood or adolescent stages of development (Lawrence, 2009). How HD is inherited HD is a disease that is passed from parents to children through misspelling or mutation in the normal gene, and it is found in every part of the world. A single abnormal gene can lead to the development of this disease. Genes are made up of deoxyribonucleic acid (DNA): which is a molecule that exists as spiral ladder (HDSA, 2008). Every strand of DNA is made up of two paired chemicals known as bases. These bases include adenine (A), thymine (T), cytosine (C) and guanine (G). Bases usually pair together, and combine with other pairs to form coded messages. Genes, therefore, exist as long strands of paired bases in various combinations. A normal human being has approximately 30, 000 genes, which determine a person’s traits and characteristics (HDSA, 2008). The effect of genes on determining an individual’s characteristics depends on whether it is dominant or recessive. When a gene is dominant, only a single chromosome is needed to produce its effect, and when it is recessive, pair of chromosome copies is required to produce a characteristic or trait. HD is a dominant disorder that is caused by a copy of a defective gene, which is inherited from one parent (HDSA, 2008). The defective gene that produces HD is a sequence of DNA on the chromosome 4, which is made up of several base pairs that repeat themselves many times. A normal gene is usually composed of three DNA bases, made up of the sequence CAG. In HD patients, this sequence normally repeats itself several times, and the number of repeats becomes larger in the subsequent generations. Parents have two copies of chromosomes each, but they only donate one copy to each child (HDSA, 2008). A ch ild born of HD parents has 50-50 chance of developing this disease. Any child, who does not inherit a copy of HD gene from parents, can never develop this condition, and he or she cannot pass it to the next generations. Children who inherit HD gene may not show symptoms of this disease in early ages, but later in their lives. It has also been shown that some people develop this condition even if there is no family history of HD. It is believed that this is caused by a new genetic mutation, a process