The polymerase chain reaction: a new method of using molecular genetics for medical diagnosis

Article Abstract:

A new method of identifying specific DNA (deoxyribonucleic acid, which comprises the body's genetic material) has been developed that can identify even single DNA molecules. The procedure uses biologic amplification of the targeted DNA so that extremely small amounts of material can be duplicated, even millions of times, to produce a quantity of material that can be fully analyzed. The method, known as the polymerase chain reaction or PCR, has been used in forensic medicine to identify an individual on the basis of a single hair shaft or sperm sample. The procedure has also allowed the development of methods for identifying the presence of the human immunodeficiency virus (HIV) in the blood of infected individuals before antibodies against the virus are able to be detected. The polymerase chain reaction was developed by scientists of the Cetus Corporation and uses specific biologic reactions to amplify the target material. The process and the necessary reagents to carry out the reaction are described. The polymerase chain reaction is useful in any situation that requires DNA to be examined, including genetics, forensic medicine, and archeology. In general the method is used to answer a critical diagnostic question: does a particular DNA segment exist? As an example, the test could be used to determine whether a hair sample found on a victim contained the same unique DNA sequence of a particular individual who is suspected of physical assault. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Polymerase chain reaction, Molecular genetics, Cetus Corp.

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The mitochondrial genome - breaking the magic circle

Article Abstract:

The nucleus of the cell contains DNA, genetic material inherited from both parents. In addition, the mitochondria, the energy producing organ of the cell, has its own separate DNA which is responsible for the production of proteins required for cellular activities. This mitochondrial DNA is contributed solely by the mother during the fertilization process. Diseases that result from mutated mitochondrial DNA can be passed to male and female children, but only daughters will continue to pass on the disease. A variety of neuromuscular diseases affecting muscle and brain function are caused by a mitochondrial gene mutation which inhibits the proper production of certain proteins. It is reported that portions of the mitochondrial DNA were deleted in some, but not all, patients with suspected mitochondrial disease. Patients having similar deletions did not necessarily have similar clinical features. It is suggested that a defect in the DNA of the cell nucleus may influence the separate DNA of the mitochondria. The mitochondrial DNA mutates easily and two independent mutations were found in the same family. Reduced activity was found in an enzyme of the respiratory chain gene in the platelets of individuals with Leber's optic neuropathy. The mechanism of disease caused by such gene mutations is unclear.

Physiological aspects, Muscle diseases, Muscular diseases, editorial, Mitochondrial myopathies

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A mitochondrial DNA mutation as a cause of Leber's hereditary optic neuropathy

Article Abstract:

Leber's optic neuropathy is a disease inherited from the mother which causes rapid loss of vision in both eyes during the late teenage and early adult years. The human cell has a nucleus which contains DNA, the genetic material, inherited from both parents. In addition, the mitochondria, the energy producing organ of the cell, has its own separate DNA which is responsible for the production of certain proteins used for cellular activities. This mitochondrial DNA is contributed solely by the mother during the fertilization process. Diseases produced as a result of mutated mitochondrial DNA can passed to both male and female children, but only daughters will pass on the disease. A variety of neuromuscular diseases are caused by a mitochondrial gene defect which inhibits the proper production of required proteins. The mitochondrial gene mutation was traced to a chromosomal deletion and the exact location on the gene was identified after three families with Leber's optic neuropathy were evaluated. The mutation is very subtle and the mechanism by which it causes blindness is unclear.

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