Medical Genetics - V. M. Zaporozhan 2005

Methods of Diagnosing Hereditary Diseases
Molecular Genetic Methods (DNA Diagnostics Methods)
DNA Microarrays

DNA Microarrays represent a rapidly advancing modern technology in biological research. The method involves depositing and immobilizing A large number of DNA probes onto the flat surface of a nylon membrane (macroarrays) or a Microscope slide (microarrays). Depending on the objective, The complexity of the array—including the number of immobilized probes and their spatial density—can vary significantly. The probes are artificially synthesized oligonucleotides complementary to either normal or mutant sequences of the DNA samples under investigation.

The DNA under study is specially prepared: target DNA fragments are pre-amplified using biotin-labeled primers. To detect a specific sequence in the test DNA sample, Hybridization is performed between the probes immobilized on the macroarray or microarray and the generated labeled PCR products. Following hybridization, the array is washed to remove unbound DNA. Hybridization results are detected by luminescence using Fluorescence Cell/15.html">Microscopy equipment and analyzed with specialized software. This entire process is automated.

Polyacrylamide gel-based microarrays have also been developed. Such an array consists of a Glass plate (microscope slide) containing gel Cells, with each cell forming a rectangular or cylindrical block. Cell dimensions may be 100x100x20 µm or smaller. A single microarray can accommodate up to several thousand such cells. Essentially, each gel cell Functions as a micro-test tube with a volume of less than one nanoliter, and the cells are isolated from one another.

A set of distinct DNA probes is introduced into the cells, and the array is used for DNA analysis in a manner analogous to the methodology described above. Polyacrylamide gel DNA microarrays are likewise employed to carry out PCR reactions. To this end, various primers are loaded into the cells, enabling the screening of test DNA for numerous Mutations simultaneously and facilitating the rapid sequencing of large DNA fragments.

DNA microarray technology enables automated and efficient analysis of a wide range of mutations and polymorphisms, as well as the evaluation of Gene Expression profiles within studied DNA. Below are several Applications of this technology in medicine: 1) determination of microbial resistance to Antibiotics (DNA microarrays allow simultaneous testing of microbial strains for numerous mutations responsible for Antibiotic Resistance); 2) Diagnosis of leukemias and other malignancies, including the Analysis of the so-called "genetic tumor profile"; 3) diagnosis of VIRAL INFECTIONS AND detection of Viruses in the environment.