cytogenetica

Cytogenetics is a branch of genetics that studies the structure and function of chromosomes and their role in heredity and disease. It combines cellular biology and genetics to analyze chromosome number, structure, and behavior during cell division. Cytogenetic analysis seeks to identify numerical abnormalities such as aneuploidies and structural rearrangements including translocations, deletions, duplications, and inversions, which can influence development and disease.

Historically, cytogenetics developed with the introduction of light microscopy, cell culture, and chromosome banding (G-banding), enabling the routine creation of metaphase spreads and human karyotypes. Modern cytogenetics employs a suite of molecular and imaging techniques: fluorescence in situ hybridization (FISH) uses fluorescent probes to detect specific DNA sequences on chromosomes; multicolor FISH and spectral karyotyping visualize multiple chromosomes simultaneously. Array-based methods such as comparative genomic hybridization (array CGH) and SNP arrays detect copy-number variations across the genome. Next-generation sequencing-based methods can identify balanced rearrangements and complex rearrangements at higher resolution. Most analyses require dividing cells, though some techniques use non-dividing cells.

Applications include prenatal diagnosis to detect aneuploidies and other chromosomal abnormalities; cancer cytogenetics to detect characteristic translocations and amplifications that guide prognosis and treatment; and research into chromosome structure, evolution, and function. Limitations include limited resolution for small variants, dependence on cell culture and sample quality, and the need for expert interpretation. Ethical considerations in genetic testing and genetic counseling are important in clinical cytogenetics.