Diagnosis genetic diseases

Restriction endonucleases facilitate diagnosis of genetic diseases by revealing restriction fragment length polymorphisms. 

If the genetic lesion is understood and a specific probe is available, prenatal diagnosis is possible. DNA from cells collected from as little as 10 mL of amniotic fluid (or by chorionic villus biopsy) can be analyzed by Southern blot transfer. A fetus with the restriction pattern AA in Figure 40-10 does not have sickle cell disease, nor is it a carrier. A fetus with the SS pattern will develop the disease. Probes are now available for this type of analysis of many genetic diseases. 

Is to determine the sex of the fetus the other Is to determine whether the fetus has a chromosome abnormality Fetal sex determination Is not, at present, performed so that couples can chose the sex of their baby While there may not be any significant ethical or sociological (43) reasons to oppose sex determination for this reason, the lack of sufficient facilities has made this an Indication of extremely low priority The reason for ascertaining the sex of a fetus. In so far as the prenatal diagnosis of genetic disease Is concerned. Is to determine Aether the fetus Is a male or female In situations In which the parents are at risk of having a child with an X-llnked disorder which affects only males If the fetus Is a male. It will have a 50% risk of being affected This risk. In such... 

Along with an effective electrolyte and screening program for genetic disease, the laboratory of Neonatology needs to have the capability of analyzing for other components in blood serum, which aid in the diagnosis of disease. These include such determinations as alkaline phosphatase, and various other enzymes, creatinine, uric acid and a host of other components which are normally assayed by the main clinical laboratory. 

Individuals at risk for developing a genetic disease with a delayed age of onset may wish to learn whether they have inherited a disease-causing mutation (e.g., Huntington disease, femilial breast cancer, hemochromatosis, adenomatous polyposis coli). In some cases, presymptomatic diagnosis can be highly usefiil in preventing serious disease consequences before they occur (e.g., phlebotomy for hemochromatosis, early tumor detection for familial breast cancer). 

This is now a routine part of prenatal care, and it will detect some malformations and genetic diseases (e.g., nearly aU cases of anencephaly, most cases of open spina bifida, some types of reduced stature conditions, many congenital heart defects). However, the sensitivity of ultrasound diagnosis is low for many conditions (e.g., Down syndrome), and it fails to detect many genetic and biochemical abnormalities. 

The measurement of enzyme activities in tissues other than blood can also be carried out, for example, in extracts of tissue obtained by biopsy, from red or white blood cells or from cerebrospinal fluid. Such measurements are valuable in diagnosis of genetic diseases in... 

As discussed above, in the case of phenylketonuria, early intervention can make the difference between mental retardation and a near normal life course for a newborn. Congenital adrenal hyperplasia and maple syrup urine disease are two examples of neonatal hereditary disorders where early diagnosis and medical intervention can make the difference between life and death for the newborn. In addition, in a number of genetic diseases, early diagnosis and treatment can help ameliorate symptoms these include fragile X syndrome, homocystinuria, sickle cell anemia, cystic fibrosis, and many /1-thalassemias. 

Kogan SC, Doherty M, Gitschier J (1987) An improved method for prenatal diagnosis of genetic diseases by analysis of amplified DNA sequences. New Engl J Med 317 985-990... 

Families with a history of severe genetic disease, such as an affected previous child or near relative, may wish to determine the presence of the disorder in a developing fetus. Prenatal diagnosis allows for an informed reproductive choice if the fetus is affected. 

Prenatal diagnosis and carrier detection of cystic fibrosis Cystic fibrosis is an autosomal recessive genetic disease resulting from mutations in the cystic fibrosis transmembrane regulator (CFTR)... 

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