Huntington’s Disease. Mechanism of Inheritance

Introduction

Huntington’s disease is also referred to as Huntington’s chorea which is an inherited disorder affecting an individual’s brain. It mainly affects the affected person’s personality, memory capabilities and mood changes. Physical control may be lost as well with most of these symptoms progressing as the disease advances. Affected individuals are eventually unable to perform basic activities such as walking, thinking and even talking to the point of being dependent on care from other people. Basically, these symptoms appear at a later age of around forty years. It involves damage of the nerve cells resulting to weakening of some segments of the human brain. This disease is not curable and it causes mental disabilities in the patients and their families may suffer emotional as well as financial disabilities (Chial, 2008, p. 1).

Inheritance of the disease

Huntington’s disease is passed from mother to her unborn child due to mutations from the normal gene. Genes are the basic biological units of life and heredity. A single mutation forms an abnormal gene which alone is enough to cause this disease. All genes are made up of either DNA or RNA but not both. Both DNA and RNA are spirally shaped molecules made up of two base pairs. The four bases, adenine, guanine, cytosine and thymine always form specific pairs which later combine to form messages in the form of codes. The unique and specific combination of these base pairs in each gene specifies the particular functions of the genes. All human beings have 23 pairs of chromosomes where the genes are arranged. Each pair of chromosomes consists of one chromosome from the mother and the other from the father. Half of the chromosome pair is similar to the other half with the exception of the sex chromosome where a female has two X chromosomes while a male has an X and a Y chromosome. Huntington’s disease is produced by mutation of the gene that is located on the 4th of the 22 chromosomes that are not sex-linked. Since the sex chromosomes are not involved in the production of this disease, both men and women are equally susceptible to Huntington’s disease (Kennard, 2006, p. 1).

Mechanism

The gene that causes huninton’s disease is dominant which means that only one mutated gene from either parent is required to produce the disease. The mutation accountable for Huntington’s disease involves a minor DNA sequence on chromosome four of the 22 autosomal chromosomes. The defect occurs when the normal base sequence, CAG is repeated severally. With each successive generation, the number of abnormal base repeats increases leading to the production of the symptoms involved in this disease. Children from a Huntington’s disease parent have 50% probability of getting the disease because each parent gives one of the two copies of every chromosome to their children. The inheritance of the disease by one child does not determine whether the other children by the same parents will inherit it or not. Only in rare cases does the disease occur sporadically as a result of new mutations of genes (McHenry, 2010, p. 1).

Prevalence

Studies had shown that Huntington’s disease is more common in the United Kingdom. A new research has confirmed that the U.K. is currently providing care to 6702 citizens with symptoms of Huntington’s disease. This means that 12 people out of each 100,000 population are affected. The prevalence seems to be increasing from the previous research that had an estimate of 6.7 cases in each 100,000 citizens (Spinney, 2010, p. 1). This estimate may even be an underestimate due to disgrace by many which affects the studies. The real prevalence, therefore, is more likely to be higher than this. Underestimation has resulted from families failing to accept that they have Huntington’s disease and the inability to test for the disease in the past although this problem has now been solved with improved techniques for its diagnosis. A very high prevalence of Huntington’s disease has been found in the lake region of Venezuela with 700 people out of 100,000 being affected. In Australia, study gives a prevalence of 6.29 in every 100,000 population with 50% people being faced with the risk of inheriting the disease (Hitt, 2010, p. 1).

Symptoms

The initial symptoms of Huntington’s disease are variable in different individuals. However, it is common in all patients for the disease to advance faster if initial symptoms had appeared early. An individual first experiences mood swings and gets irritated for no particular reason. The person may not notice these early symptoms but the family members do. The affected person feels depressed and lacks the will and general lack of interest in almost everything. In some individuals, these symptoms may reduce as the disease advances while in others, they may continue accompanied by sudden violent disturbances. Due to the memory loss associated with Huntington’s disease, the patient may experience trouble learning new things and in performing basic tasks such as driving. Remembering usual things and making decisions becomes a problem as well. Others may change their handwriting and lose their ability to comprehend. Other individuals experience uncontrolled movement of fingers and feet which often get more vigorous when the affected person is anxious. Loss of balance is also a very common initial sign of Huntington’s disease increasing the chances of the individual to fall when walking. With time, it reaches a point where individuals are unable to eat, talk or even recognize their family members (Appai-Kubi, and Chaudhuri, 2001, p. 1).

Treatment

Currently, there is no treatment that can stop or even slow the disease. The main idea of treatment is basically the management of the signs and effects of the disease. Medications have been produced to ease the spontaneous movements and disturbing disorders although some patients may experience certain side effects such as drowsiness and nausea during which they should terminate the use of that particular medicine. Patients experiencing psychological symptoms are recommended to use anti-depressant medications. Besides medical assistance, physical therapy is necessary to help keep balance and build strength for walking and other activities. The time spend during exercise also helps in reduce depression as the patient gets pre occupied (Martin, 2010, p. 1). Use of care givers to assist in helping such patients is necessary especially where one has a lot of chores and other things to take care of. This is because the patients require extra attention and they may also need the use of long-time facilities. Huntington’s disease cannot be prevented since it occurs naturally through inheritance. The disease is also not curable and therefore patients should be given all the support they need from family members as well as the society. However, scientists have recently found out that there are some synthetic chemicals that can interfere with the production of protein and prevent human cells from producing mutated molecules that result to development of the disease.

Bibliography

Appai-Kubi, L. and Chaudhuri, R. (2001). Huntington’s disease. Web.

Chial, H. (2008). Huntington’s Disease: The Discovery of the Huntingtin Gene. Web.

Hitt, E. (2010). Prevalence of Huntington’s Disease Underestimated. Web.

Kennard, C. (2006). Huntington’s Disease. Web.

Martin, C. (2010). IT’S THOSE ANNOYING CAG REPEATS. Web.

McHenry, R. (2010). Learning About Huntington’s Disease. Web.

Spinney, L. (2010). Uncovering the true prevalence of Huntington’s disease. Web.

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NerdyRoo. (2022, March 23). Huntington’s Disease. Mechanism of Inheritance. Retrieved from https://nerdyroo.com/huntingtons-disease-mechanism-of-inheritance/

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