karyotipe

Karyotype, sometimes written as karyotipe in some languages, is the complete set of chromosomes in an individual or cell, organized by size, structure, and number in a standardized display. The term derives from Greek karyon meaning kernel or nucleus and typos meaning model or form. A karyotype provides a snapshot of chromosomal constitution and is a fundamental tool in medical genetics, cytogenetics, and comparative genomics.

Preparation and methods: To produce a karyotype, cells are cultured and arrested in metaphase, then stained and photographed. Chromosomes are arranged into homologous pairs and ordered by size to create a karyogram. Traditional methods use G-banding to reveal characteristic light and dark bands; newer approaches include high-resolution banding, spectral karyotyping with multicolor FISH, and targeted techniques.

Applications: Karyotypes are used to detect numerical abnormalities such as aneuploidies (extra or missing chromosomes) and structural rearrangements (translocations, deletions, duplications, inversions). They help diagnose conditions such as Down syndrome, Turner syndrome, Klinefelter syndrome, and other sex-chromosome anomalies. They are also used in prenatal testing, fertility assessment, cancer cytogenetics, and species comparison.

Normal human karyotype examples: 46,XX for a typical female and 46,XY for a typical male. Common abnormalities include trisomy 21 (47,XX+21 or 47,XY+21), monosomy X (45,X), and various sex-chromosome or autosomal alterations. Karyotyping has limited resolution and may miss small copy-number variants; more sensitive techniques like array CGH or sequencing can detect smaller changes.

In research and agriculture, karyotypes are used to study evolution, speciation, and breeding, since chromosome number and structure reflect phylogenetic relationships and genome rearrangements.