Karyotype (Chromosome Analysis)
Definition
Examines the number, size and shape of the chromosomes in a cell sample. It shows whether a person has the 46 chromosomes (23 pairs) that are typically expected and whether any structural abnormality is present.
Purpose
Screening for chromosomal abnormalities during family planning, in pregnancy, or in the investigation of infertility, recurrent miscarriages or suspected genetic conditions.
Results
What it can detect:
| Type | Example |
|---|---|
| Numerical abnormality | Down syndrome (extra chromosome 21), Turner syndrome (missing X chromosome) |
| Structural change | Deletion, duplication, translocation, inversion |
| Cancer-related | Abnormal chromosome patterns in leukemia, lymphoma and blood disorders |
How a normal result is written: 46 chromosomes in the sample with no unusual change in their structure → 46,XX (female) or 46,XY (male)
Risks and Limitations
What a karyotype cannot see:
The test cannot detect single-gene disorders or DNA changes at the submicroscopic level. It shows only large-scale chromosomal changes that are visible on standard cytogenetic examination.
In other words, a normal karyotype does not mean there is no genetic disease. Small deletions require FISH or microarray, and single-gene disorders require sequence analysis (WES/WGS).