Karyotípus

Karyotípus is the number and appearance of chromosomes in the nucleus of a cell. It is typically represented as a karyogram, a visual arrangement of chromosomes ordered by size, centromere position, and banding pattern. A karyotípus reflects both the chromosomal complement and structural features such as translocations, deletions, inversions, or duplications.

In humans, somatic cells normally contain 46 chromosomes: 22 autosome pairs and 1 pair of sex chromosomes (XX in females and XY in males). The karyotípus can reveal numerical abnormalities (aneuploidy, polyploidy) as well as structural rearrangements that may have diagnostic or prognostic significance. Common examples include trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), trisomy 13 (Patau syndrome), Turner syndrome (monosomy X), Klinefelter syndrome (47, XXY), and other sex-chromosome variations.

Obtaining a karyotípus involves culturing cells (often lymphocytes or fetal cells) to obtain metaphase chromosomes. Cells are treated to arrest mitosis, fixed, stained, and photographed. G-banding and other banding techniques reveal characteristic patterns that allow identification of each chromosome and any large-scale abnormalities. High-resolution banding and digital imaging improve detection, while newer methods may provide sharper detail or complementary data.

Applications include prenatal diagnosis through amniocentesis or chorionic villus sampling, investigation of infertility, and cancer cytogenetics, where clonal chromosomal changes inform classification and management. Limitations include limited resolution for submicroscopic changes and inability to detect single-nucleotide variants; chromosomal microarray or sequencing may be used alongside karyotípus analysis for a more comprehensive genome assessment.