Looking at all the chromosomes at once reveals numerical and structural problems. A karyotype is a visual arrangement of an individual’s chromosomes, ordered by size and banding pattern. Cells are arrested in metaphase, stained, photographed, and the chromosomes paired and numbered.

A normal human karyotype shows 46 chromosomes: 22 pairs of autosomes and two sex chromosomes. Extra or missing chromosomes, large deletions, duplications, and translocations become visible. High-resolution banding and newer molecular methods increase the detail that can be observed.

Clinical cytogenetics laboratories produce karyotypes to diagnose aneuploidies, unbalanced rearrangements, and some cancers. The image provides a genome-wide view at low resolution and remains a frontline test for many developmental and reproductive questions.

• Visual display of an organism’s chromosomes
• Arranged by size and banding pattern
• Detects numerical and large structural changes
• Used in clinical cytogenetic diagnosis