Fundamentals of Medical Genetics - Buzhyievska T.I. 2001

Methods of Genetic Examination
Laboratory Medical and Genetic Methods

Laboratory Medical and Genetic screening Methods feature high sensitivity, enabling the definitive determination of a Diagnosis, as well as The Nature and localization of a hereditary defect at the level of Gene products, Gene Mutations, Chromosomes, or the entire genome.

These methods are indispensable for mass pathology screening, invasive prenatal diagnosis, detection of pathological allele carriers, paternity testing, and preclinical diagnosis of diseases.

In this guide, we will limit ourselves to a Brief Overview of these methods, as their detailed exploration is the subject of specialized monographs and textbooks utilized by clinical laboratory geneticists.

The cytogenetic method is used to investigate chromosome number and structural quality, detect chromosomal abnormalities and mosaicism, and identify carriers of balanced Chromosomal aberrations. Variants of this approach include various chromosome banding techniques utilizing fluorescent and radioactive markers, alongside Molecular-Cytogenetic Methods (such as in situ Hybridization and the FISH assay).

Thanks to the application of this method, an increasing number of human developmental pathologies are transitioning from the category of idiopathic, sporadic disorders to the group of chromosomal and inherited conditions.

Specialized Biochemical Methods are designed to detect specific products of impaired Gene Expression—such as free Amino Acids, Lipids, Glycoproteins, CARBOHYDRATES, Enzymes and their inhibitors, abnormal metabolites in Blood, urine, body Tissues and Cells, Amniotic Fluid, chorion, etc.—as well as mineral imbalances.

The Dermatoglyphic method involves The Study of epidermal ridges, lines, and creases on the palms, soles, and palmar surfaces of the fingers. While this technique is thoroughly mastered by fortune tellers, seers, and gypsies, it remains relatively unfamiliar to physicians. At the same time, the simultaneous embryonic development of Skin patterns on these body regions and Brain structures suggests that dermatoglyphics holds significant potential yet to be widely applied in medical practice.

Microbiological methods are used to detect metabolic products in patient specimens by measuring the ability of dependent microorganisms (auxotrophs) to proliferate in their presence, as is the case in phenylketonuria.

Molecular-Genetic Methods make it possible to diagnose the carrier state of a specific allele (including a mutant one) at the DNA codon domain level, even in the absence of gene expression products, and to determine whether an individual is homozygous or heterozygous. The core of these methods relies on the Specificity of nucleic acid-cleaving enzymes, THE PRINCIPLE OF nucleotide sequence complementarity, the selective Replication and Amplification of double-stranded DNA segments, and The ability to synthesize missing structural fragments *in vitro* rather than within a Cell or Organism. This specific group of techniques holds the greatest promise for solving problems in prenatal, preimplantation, and even preconception diagnosis, as well as for paternity testing and forensic identification. These versatile, specialized methods can be effectively integrated into healthcare practice, provided there is adequate funding. The sole drawback of molecular-genetic methods is their high cost.

In the fields of human and medical genetics, population, variation-statistical, and twin studies are also widely employed; these methods allow researchers to investigate the respective roles of HEREDITY AND ENVIRONMENT in disease development, the prevalence of hereditary pathology and pathological allele carriers within specific populations, and to assess The Significance of segregation load and mutation pressure.