A karyotype is a picture of all the chromosomes from an individual’s cells. A karyotype is a test used to check for chromosome abnormalities. A picture of a person’s chromosomes is created by staining the chromosomes with a special dye, photographing them through a microscope and arranging them in pairs. A karyotype gives information about the number of chromosomes a person has, the structure of their chromosomes and the sex of the individual. Down syndrome is diagnosed by a karyotype test.