A Genetic Disorder: Tay-Sachs Disease Essay Sample
Most infants born with normally developed motor functions have the ability to synthesize specific enzymes necessary for a healthy growth process. But babies inflicted with a rare genetic disorder called Tay-Sachs disease experience motor dysfunction due to the continuous degradation of their central nervous system. This disorder is detectable prior a child’s birth, and it is possible to compute for the probability of a newborn phenotypically manifesting the disease. However, at present, experts are yet to discover the proper treatment for this condition (Lowden 575).
Tay-Sachs disorder is typically found among Ashkenazi Jews from Eastern Europe. But other population also manifest this metabolic disorder, including the Cajuns of Southwestern Louisiana and the French Canadians of Southeastern Quebec. It is normally manifested by a defined population, where patients acquire their disease through genetic inheritance. Tay-Sachs is an autosomal recessive disorder manifested due to a defect on an individual’s chromosome number 15 leading to a defect in the function of the lysosome organelle. This mutation results in an individual’s failure to direct its lysosome to properly synthesize the enzyme acid hydrolase. This consequently leads to the enzymatic dysfunction of Beta Hexosaminidase A, which is has a vital impact on the lysosomal storage function (Ohno and Suzuki 18563; Genes and Disease 23).
This genetic disease primarily arises due to the modification, specifically a point mutation, of the alpha subunit, which leads to the failure of β-N-Hexosaminidase A to proceed its normal activity. This abnormality found in the alpha subunit is related to the 5′ end, where mutations including insertions and deletion of base pairs occur. In every form of modification occurring, protein products are altered. These alterations cause enzymatic function inhibition, and therefore cellular dysfunction. In the case of the Ashkenazi Jews, the said mutation is commonly found at exon 11, where four base pairs are inserted. Due to the mentioned mutations, Ganglioside GM2 enzymes are instead synthesized. The cell does not possess the ability to degrade these enzymes, and therefore accumulate the latter instead. These granular bodies are typically detected through microscopic examinations of neuronal bodies, furthermore reinforcing the presence of the disorder. Because of these glycogen lipid accumulations, the neurons’ myelin sheaths are destroyed thereby causing the various symptoms and different clinical manifestations of the disease (Li et al. 10014; Van de Graaff 370).
This disease is commonly the result of the passing of this chromosomal defect from parent to offspring. Tay-Sachs disease is a recessive disorder, therefore it is only manifested when a child acquires both alleles coding for the disorder. Heterozygous offspring only carry one allele, therefore are only considered carriers of the disorder. They are not afflicted and will continue to function normally. The normal allele can compensate for the impairment of the other. However these carrier individuals possess the ability to pass the genes to their children (Branda et al. 174).
Manifestations of Tay-Sachs disease among afflicted individuals have varying degree of severity. This can cause “paralysis, dementia, and early death to a chronic adult form” (Genes and Disease 23). The mentioned adults are frequently observed to suffer from psychosis and neural dysfunctions (Genes and Disease 23).
Some of the other typical manifestations of Tay-Sachs are infantile blindness and deafness. Newborns afflicted with the disorder often undergo normal development during three to six months of age, after which they continuously suffer from mental retardation. They encounter motor deterioration, resulting in failure of developing their motor abilities. Then after one year, they also suffer from physical complications including dysphagia, chest and lung failure (Hauser 2171).
One of the most renowned symptoms of Tay-Sachs is the cherry-red macular spots, as their fovea centralis becomes highly pronounced, commonly found among patients. Babies have delayed motor development, demonstrated by their poor management of head control, inability to crawl, sit, and recognize visual cues. Children become unresponsive to their environment, as they lose visual focus and eye contact. They are unable to develop reflexive responses towards external stimuli, seen as inattention and vegetative regression. Other common symptoms include hyperacusis, seizure, and macrocephaly (Kasper et al 2318).
Tay-Sachs can be manifested by different ages, as it affects patients are young as three months and as old as 15 years. This disorder is classified according to the age it afflicts a patient, including classic infantile, juvenile, and adult form. Classic Infantile patients are babies that are born with the disease as they completely lack the ability to produce the enzyme Hexosaminidase A. They normally do not live more than five years, as they suffer from paralysis and muscle atrophy. Juvenile patients manifest the disorder from two to ten years of age, and undergo a relatively slower process of deterioration. Dysarthria, dysphagia, and ataxia are common symptoms among juvenile patients. Patients normally do not survive more than 15 years of age. Adult form of this disease is found to have milder effects among patients, which is primarily the reason for the longer survival of individuals. This has a relatively late onset in life and is considered a chronic disorder. Symptoms normally appear during the patient’s adolescent stage, where one experiences blindness or deafness. However not completely mentally degenerated, patients still suffer form mental weaknesses. There is no definite life expectancy for adult Tay-Sachs patients (Tay-Sachs disease no page).
There is no available effective cure for Tay-Sachs patients. Scientists are currently under the process of determining which of the proposed procedures, such as stem cells and enzyme replacement therapy, is the most appropriate form of treatment (Escolar et al., 2; Bembi 278; Tay-Sachs disease no page). However, carrier parents can avail of prenatal tests such as amniocentesis and chorionic villus sampling. Both of these examinations determine the presence of the disease before an infant is born. In the case of amniocentesis, this procedure is normally conducted between 15th and 20th pregnancy week. This is done by inserting a needle into the abdominal portion of the mother in order to collect samples of amniotic fluid. If this sample is found to positively posses β-N-Hexosaminidase A, then the baby is declared to possess the disorder. The chorionic villus sampling, on the other hand, is done during the 10th and 12th week of pregnancy. Here, placental cells are retrieved through inserting a tube into the mother’s vagina or by inserting a needle into the mother’s abdomen. This has the same objective of detecting the presence of β-N-Hexosaminidase A in order to determine whether the patient is suffering from Tay-Sachs disease (Tay-Sachs disease no page).
Although patients plagued with Tay-Sachs disease still do not have chances to lead a normal life, there are promising research studies that scientists are conducting. Their results reveal tremendous possibilities that humans can combat this disease through prevention and even treatment. Therefore, despite this daunting condition, humans can fight this disorder through participating in various screening processes that would enable them to calculate the probability of giving birth to an afflicted offspring (Lowden 575).
Bembi, B. “Substrate Reduction Therapy in the Infantile Form of Tay-Sachs Disease.”
Neurology, 66 (2006): 278-280.
Branda KJ, Tomczak J, Natowicz, MR. 2004. “Heterozygosity for Tay-Sachs and Sandhoff
diseases in non-Jewish Americans with ancestry from Ireland, Great Britain, or Italy.” Genet Test 8 (2004):174-180
Escolar, Maria L., Michele D. Poe, James M. Provenzale, Karen C., Richards, M.D., June Allison, R.N., Susan Wood, P.N.P., David A. Wenger, Daniel Pietryga, Donna Wall, Martin Champagne, Richard Morse, William Krivit and Joanne Kurtzberg, M.D. “Transplantation of Umbilical-Cord Blood in Babies with Infantile Krabbe’s Disease.” The New England Journal of Medicine, 352 (2005):2069-2081.
“Genes and Disease.” Bethesda (MD): National Library of Medicine (US), NCBI. 29 January
Hauser SL, Longo DL, Harrison’s Principles of Internal Medicine. Ed.14th ed. New York: McGraw-Hill; 1998; p. 2171.
Kasper, D. L., A. S. Fauci, D. L. Longo, E.Baraunwald, S. Hauser, S. L .Jameson, Harrison’s Principles of Internal Medicine 16th Ed. USA: McGraw-Hill Companies, Inc. 2005.
Li, Y., S. Li, , A. Hasegawa, H. Ishida, M. Kiso, A. Bernardi, P. Brocca, L. Raimondi, and S. Sonnino. “Structural basis for the resistance of Tay-Sachs Ganglioside GM2 to enzymatic degradation.” The Journal of Biological Chemistry, 274:10014-10018, 1999.
Lowden, J. A. “Role of the physician in screening for carriers of Tay-Sachs disease.” CMA Journal 119 (1978):575-585.
“Tay-Sachs Disease.” 29 January 2008 <http://www.marchofdimes.com/professionals/14332_1227.asp>.
Ohno, K. and K. Suzuki. “Multiple Abnormal β-N-Hexosaminidase A α Chain in mRNAs in a Compound Heterozygous Ashkenazi Jewish Patient with Tay-Sachs Disease.” The
Journal of Biological Chemistry, 263:18563-18667, 1988.
Van de Graaff, K. M. andS.I. Fox, Human Anatomy and Physiology. Iowa: Wm. C. Brown Publishers.