Genetic Disorders

Chromosomal analysis can be performed on cell samples from an individual, a technique called karyotyping. A karyotype involves visualizing the chromosomes using a specific dye and a high-resolution microscope. The chromosomes can be distinguished from one another in size and staining pattern. Corresponding chromosomes 1 through 22 and the sex chromosomes can be lined up and visually inspected for abnormalities. Any obvious defect can indicate a diseased state. Sometimes it is apparent that a part of one chromosome was incorrectly combined with a different chromosome during cellular division. This is called a translocation and represents a structural abnormality. Numerical abnormalities occur when an extra chromosome is present. When more than 46 chromosomes are observed in chromosome, it is called aneuploidy. Most aneuploidies that occur are called trisomies which involve three homologous chromosomes, or the presence of extra chromosome. Numerical abnormalities are typically incompatible with life, with the exception of Trisomy 21 (Down Syndrome) and a few other rare genetic disorders.