Prenatal Diagnosis Essay Research Paper Prenatel DianosisHeredity

Prenatal Diagnosis Essay, Research Paper

Prenatel DianosisHeredity Disorders, Other Biochemical Diseases, and Disfiguring Birth DefectsThere are over 250 recognized sex-linked diseases, affecting every organ system.Of these, 95% affect males, (Emery, 1968). Despite these many sex-linked diseases, atpresent prenatal diagnosis can specifically be made in fewer than 40 diseases. (Emery,1968). These sex-linked diseases are individual rare and some are named afterphysicians who described them, for example, Hemophilia A and B, Duchenne musculardystrophy, fragile-X syndrome, Fabry disease, Hunter syndrome, Lesch-Nyhan syndrome,and Menkes steely-hair syndrome. The following discourse considers the reasons for theimportance of prenatal diagnosis, heredity disorders, and disfiguring birthdefects.(Nora,1989). Fabry disease is a biochemical disorder caused by a missing enzyme. (Mulinsky,1989). A complex fatty substance accumulates in the body because of the missingenzyme which would ordinarily break this compound into pieces.(Nora,1989). Thismissing enzyme causes kidney and blood-vessel problems that lead to high bloodpressure, kidney failure and strokes.(Mulinsky, 1989). After many years of symptoms,most patients have died in their thirties and forties owing to a lack specific treatment. A biochemical disorder also caused by a missing enzyme is the Lesch-Nyhansyndrome, an extremely unpleasant disorder characterized not only by profound mentalretardation and features of brain damage (stiff limbs with peculiar movements), but alsoself-mutilation, (Jones, 1988). Given good care and attention however, these patientsmay live on many years in their profoundly retarded state. They often require restraining,tying their hands, to prevent them from mutilating themselves. Another Affected children with Menkes steely-hair syndrome have hair that feelssimilar to steel wool; in addition, they are retarded. The basic defect in this conditionconcerns the way the body handles copper. Only a few of these sex-linked disorders can now be diagnosed in the fetus,(Stein, 1994). At the present time, the only recourse parents have in the case of sex-linked diseases that are not prenatally diagnosable is to determine the sex of the fetus. Ifa female fetus is found, the parents can be reassured that their child will not be affected(a critical exception is fragile-X). However, if it is determined that there is a male fetuspresent, there is a fifty percent chance that it is affected, (Milunsky, 1989). Since there isno way of being certain, the parents must decide simply on the basis of high risk weatherto take a chance or terminate that pregnancy. There are some unusual sex-linked diseases that are confined to females.Disorders of this kind (such as incontinentia pigmenti, a skin disorder associated withbrain damage) can be managed by determining weather the fetus is a female. In thisgroup, virtually all females will be affected, and the parents could selective elect to haveunaffected boys. Hemophilia A and Duchenne muscular dystrophy are two of the most commonsex-linked diseases that are familiar to most people. But there are so many other diseasesthat great care must be taken by both the doctor and the family in obtaining an accuratefamily history. Renpenning syndrome, in which there is mental retardation without anyother physical signs, is confined to males. The only way to suspect sex-linkedinheritance is for the physician to carefully analyze the family lineage. Tests arepreformed to detect female carriers of such diseases. For example, almost all carriers ofhemophilia and Duchenne muscular dystrophy can now be detected. A muscle enzyme,creatine phosphokinase, which leaks into the blood is also often measured to give ahigher probability of recognizing a carrier. Unfortunately, because of recombination, thecarrier-detection tests for both hemophilia and muscular dystrophy do not provideanswers in 100 percent of cases. A negative result causes uncertainty and leaves thequestion of carrier detection basically unanswered. Fortunately, carrier-detection testsare steadily becoming possible in more of the sex-linked and other disorders. Prenatal Studies for Heredity Biochemical Disorders Many hundreds of different hereditary biochemical disorders of metabolism areknown. About 1 in every 100 children born have one of these biochemical disorders. (Nora, 1989). Many of these disorders do not cause mental retardation, or impair thechild’s normal development or general health to any great extent, if at all. Many others,however, cause severe mental retardation, seizures, stunting of growth, and early death.Close to 150 of these biochemical disorders can now be diagnosed in the affected fetusearly in pregnancy. (Nora,1989). The first diagnosis of a biochemical disorder in thefetus while in the womb was made in the late 1960’s; the disorder was Tay-Sachs disease. (Emery, 1968). Diagnosis such as this are made by obtaining cells from the amnioticfluid which are placed in small dishes containing a nutrient broth, and then kept in aspecial warm, moist incubator. They grow slowly. After a period of two to three weeksor, occasionally, as long as six weeks, there are enough cells to work on. Each of thecells having the genetic blueprint will show the specific biochemical defect ( forexample, deficient activity of an enzyme) thereby enabling a diagnoses to be made. Withdiagnosis, physicians can treat the known disorder through the womb.For