Introduction There are many genetic diseases in the world. All genetic diseases are inherited from one's parents. Through Gregor Mendel's studies of genetics, it is possible for people to determine whether or not an individual will inherit a genetic disease. All genetic disorders are recessive traits (Campbell). We have learned that if a parent has a genetic disease and the other parent does not have a genetic disease, all of their children will be carriers, or have the trait, of the disease. If both parents are carriers of a genetic disease, one out of the four children will get the disease.

Some of the most common genetic disorders today are sickle cell anemia, muscular dystrophy, cystic fibrosis, hemophilia, and Tay-Sachs disease. Most of the diseases usually is predominant in a race of people or in gender (Campbell). Today through modern technology, we are able to detect whether a child will have a genetic disease through the methods of amniocentesis and chorionic villa sample (Campbell). One of the genetic disorders that doesn't receive a lot of attention is Tay-Sachs disease. Tay-Sachs can be very lethal. Discussion What is Tay-Sachs Disease Tay-Sachs Disease is a birth defect caused by a dysfunctional enzyme that fails to breakdown group of brain lipids, or fat (Campbell).

The cause of the dysfunctional enzyme is caused by a deficiency of an enzyme called Hexosaminidase A, or Hex A which is suppose to break down fatty substances in the nerve cells of the brain. When the lipids, or fats, builds up in the brains nerve cells, it leads to a slow degeneration of the cells of the nervous system, thus bringing decay of the cerebellum. This deterioration can be view on Magnetic Resonance Imaging (MRI) (webknx. com). The fatty substance that Hex A does not break down is called ganglioside GM 2. Ganglioside GM 2 accumulates on the brain cells and cannot be broken down.

Ganglioside ar made and bio-degraded quickly in the early development of the brain (web). When Hex A activity is insufficient, accumulation of ganglioside GM 2 in the neurons affects the functioning of the nervous system. How is Tay-Sachs Transmitted Tay-Sachs disease, unlike other diseases, is transmitted by a person's genetic make up. Tay- Sachs can only be transmitted if a person has both recessive alleles for the trait (Campbell).

In order for a child to get Tay-Sachs his or her parents must be carriers of the Tay-Sachs gene. Tay-Sachs carriers are not afflicted with Tay-Sachs. They can live normal and heathy lives (www. noah). If at least one parent is a carrier of the disease, two out of four off the offspring will be a carrier of the disease.

If both parents are carriers of the disease, one out of four children will not be a carrier, two out of four of the children will be a carriers of the disease, and on out of four of the children will actually have the Tay-Sachs disease (www. webknx). Figure 1 (www. m rcr 2) is a table that shows how two carries for Tay-Sachs disease can pass either Tay-Sachs trait or Tay-Sachs Disease to their children.

Figure 1 Who Gets Tay-Sachs Disease Tay-Sachs Disease is common among people of Eastern Europeans (Ashkenazi) Jewish decent, Cajun, and French-Canadian decent (www. noah). Although some people of French-Canadian and Cajun ancestry get Tay-Sachs, the disease is predominantly found among Ashkenazi Jews. In the United States, approximately one out of sixty thousand people who have the Tay-Sachs disease are in the Jewish population while one out of fourteen thousand are afflicted with Tay-Sachs in Israel About one out of thirty Jews in America carriers the Tay-Sachs disease trait (www. webknx). Are there Different Forms of the Tay-Sachs disease There are different forms of Tay-Sachs.

There is the common infantile Tay-Sachs, commonly called juvenile Tay-Sachs. In infantile Tay-Sachs the enzyme Hex A is not present to break down lipids in the brain cells. The other form of Tay-Sachs is the adult onset of Tay-Sachs. Adult onset of Tay-Sachs differs from infantile Tay-Sachs because there are low levels of Hex A enzyme in the brain cells.

But like infantile Tay-Sachs, adult onset of Tay-Sachs still cause deterioration of the brain cells. In infantile Tay-Sachs, the child affected usually dies around the fifth year of their lives. People with adult onset Tay-Sachs usually die around their fifteenth birthday (www. noah). What Are the Symptoms of Tay-Sachs Disease Symptoms of Tay-Sachs Disease can be painful and difficult to deal with. Most of the symptoms of Tay-Sachs are physical symptoms.

These symptoms can consist of hand tremors, clumsiness, speech impediments, swallowing difficulties, problems with gait and balance, and muscle weakness. Other problems with Tay-Sachs included mood alterations, abnormal behavior, Muscular Dystrophy, Multiple Sclerosis, and Amyotrophic Lateral Sclerosis. Not all symptoms of Tay-Sachs are physical (www. webknx). Most patient with Tay-Sachs develop mental illness and suffer from psychological problems. Psychological symptoms of Tay-Sachs are memory impairment, difficulty in comprehension skills, and poor performance in school.

Loss of memory is very common among Tay-Sachs patients (www. webknx 1). Infants who inherit the Tay-Sachs Disease usually have a shut down of their nervous system. First signs of a infant having Tay-Sachs diseases are gradually loss of smiling, crawling, turning over, loss of ability to grasp objects, blindness, paralysis, and unawareness of surroundings (www. noah). How Can a Person Find Out if They Are a Carrier of Tay-Sachs Disease A person can find out whether or not they are carrier of the Tay-Sachs Disease by seeing a geneticist.

The geneticist would take sample of a person's DNA and analyze it for the enzymes hexosaminidase A and hexosaminidase B. The geneticist would then look for mutations in the two enzymes. If a mutation is found, the person is possibly a carrier for Tay-Sachs Disease (Triggs- Raine). How Can One Find Out if Their Child would Have or Be a Carrier of The Tay-Sachs Disease If an expectant mother wants to know if her child will have Tay-Sachs or be a carrier of the disease, she would go see her obstetrician for genetic screening.

The obstetrician will either perform an amniocentesis or chorionic villus sampling, or CVS (Campbell and www. noah). In amniocentesis, which is usually done between the fifteenth and eighteenth week of pregnancy, a needle is inserted into the mother's abdomen to take sample of the amnion fluid that surrounds the fetus. The fluid contains fetal cells that can be examined for the presence of the enzyme hex A.

In CVS, which is usually done during the tenth to twelfth week of pregnancy, the doctor would take samples of cells either through a thin tube inserted through the vagina and cervix to the placenta or by inserting a long needle through the mother's stomach. Like the amniotic fluid, the placenta cells contain hex A (www. noah). Amniocentesis is done by centrifuging the amniotic fluid, saving the pellet for a culture to be karyotype d. This method is time consuming whereas with CVS the results of the karyotyping can be revealed within twenty four hours (Campbell). Are there Any Recent Scientific Studies on Tay-Sachs Disease Although Tay-Sachs Disease is not mention as much as other genetic disorders, such as sickle cell anemia, there is recent research being done on Tay-Sachs.

There was a test done to screen carrier of the Tay-Sachs disease. The test consisted of a comparison of DNA-based and enzyme-based tests. In the tests, scientist looked for the substance ganglioside GM 2 in each of it's subjects. They then compared the enzyme-based test with the DNA based test. After comparing the analysis of both tests, the scientists concluded that there were three mutations of Tay-Sachs Disease.

Two of the mutations cause infantile Tay-Sachs and the third was adult onset of Tay-Sachs. The mutation of Tay-Sachs were found on the DNA polymerase chains (Triggs- Raine). The DNA- and enzyme-based tests were performed on about sixty-two Ashkenazi Jews who carried the gene for Tay-Sachs. The report didn't state whether the people being tested actually had Tay-Sachs or if they just carried the gene for Tay-Sachs. Ninety percent of the people tested had all three of the mutant strands of Tay-Sachs Disease. The DNA-based test proved to show whether a person carried the three of the mutations Tay-Sachs Disease better than the enzyme-based test (Triggs-Raine).

Conclusion Tay-Sachs Disease is a genetic disorder that cannot be corrected, at least not in this present time. Although there are now ways for a person to have genetic screening to see if they have Tay- Sachs or if they are a carrier of Tay-Sachs, they still have to live with the possibility that they might pass on the genetic disorder to their children. It maybe a one out of four chance that a couple who both have the Tay-Sachs carrier gene might have a child with Tay-Sachs, but that is a risky chance to make. Maybe with future technology, scientist would be able to find a way to reverse the mutations of the Tay-Sachs Disease gene. Works Cited Page Primary Source 1. ) Triggs-Raine, B.

L. "Screening For Carriers of Tay-Sachs Disease Among Ashkenazi Jews: A Comparison of DNA-based and Enzyme-based Tests." The New England Journal of Medicine. 5 July 1990 v 323 n 1 pp 6-12. (Found through Internet search Tay-Sachs disease. In depth information on Tay-Sachs testing. ) Journals 2.

) Bradley, David. "Weighing Up Tay-Sachs Disease." Analytical Chemistry. 1 July 1998 v 70 n 13 p 443 A. (Found through Cleveland Public Library Infotrack. ) 3.

) Eng, Christine MD. "Prenatal Genetic Carrier Testing Using Triple Disease Screening." JAMA. 15 October 1997 v 278 n 15 pp 1268-1272. (Found in Cleveland Public Library Infotrack. This article just gave background but not in depth details on genetic testing for Tay-Sachs Disease and Cystic Fibrosis. ) 4.

) Motulsky, Arno G. "Screening For Genetic Diseases (Editorial)." The New England Journal of Medicine. 1 May 1997 v 336 n 18 pp 1314-1317. (Found through Cleveland Public Library Infotrack. Gave general information on gene mutations.

) Internet Sources 5. ) web (Found through Yahoo. com) 6. ) www. noah, cuny.

edu / pregnancy /marchofdimes / birth defects /tay sachs. htm (Found through Yahoo. com) 7. ) web (Found through Yahoo. com) 8. ) web (Found through Yahoo.

com) Other Sources 9. ) Campbell, Neil A. Biology. The Benjamin/Cummings Publishing Company Inc. California, 1996. (Gave general information on Tay-Sachs, amniocentesis, and CVS.

) 10. ) Acker, Bonnie and Lois Alix. The New Bodies, Ourselves. Touchstone Publishing Company. New York, 1992. (Gave general information on amniocentesis and CVS.

Did not use in report because I felt that the information was too vague and not in depth. ) 11. ) The Student Reference Library (Computer Software. Information I found on the CD Rom was an overview of Tay-Sachs disease.

It only gave a definition of what Tach-Sachs disease was and didn't dive a full in depth explanation of what the disease does to the brain. ).