The analysis of genes and their associated disorders, particularly in the context of genetic diseases, is considered an integral part of medical genetic services. Results from molecular tests can be utilized for carrier screening and prenatal diagnosis. The foundation of these tests involves DNA extraction from nucleated cells such as white blood cells, amniotic fluid, chorionic villi, and fibroblasts. Subsequently, depending on the specific disorder, targeted molecular tests are employed for diagnosis.
A genetic test is a medical test that identifies variations in genes, chromosomes, or proteins. The results can confirm or exclude a suspected genetic disorder, or determine the likelihood of developing or transmitting a genetic condition. Currently, thousands of genetic tests are available, with many more under development.
The entire genome, or the DNA content of eukaryotic cells, is organized into structures called chromosomes. The scientific study of chromosomes is known as cytogenetics. Any alteration in the number or structure of chromosomes—resulting from changes in the genetic material, gene expression, or protein production—can lead to developmental or functional disorders. Chromosomal alterations may be inherited from parents, but most occur during gametogenesis (sperm and egg formation) or at the moment of fertilization and early embryogenesis.
Chromosomal abnormalities have been observed in approximately 25% of mature oocytes and 10% of sperm. Most embryos with a complete loss or gain of a chromosome or an entire set of chromosomes are lost during early development, leading to miscarriage. Chromosomal disorders underlie many genetic diseases, including genetic syndromes (e.g., Down syndrome), congenital anomalies, intellectual disabilities, infertility, recurrent miscarriage, and, in some cases, cancer. Therefore, chromosomal analysis is highly recommended for individuals with these conditions, those with a relevant family history, and couples considering consanguineous marriage.
Cytogenetic laboratory services include:
Prenatal diagnosis: amniotic fluid and chorionic villus samples
Postnatal diagnosis: blood and tissue samples
Cancer diagnostics: blood, bone marrow, and tissue samples
These analyses are performed using cell culture, staining, image processing, and karyotyping techniques.
To complement cytogenetics and cell culture services, the laboratory also offers molecular cytogenetics, including array-based Comparative Genomic Hybridization (aCGH). This high-resolution method allows the detection of small genomic deletions and duplications as well as chromosomal imbalances. It is particularly useful for diagnosing conditions such as developmental delay, autism spectrum disorder, congenital imbalances, and intellectual or physical disabilities resulting from genomic alterations.
