This karyotype is from a woman with 45 chromosomes and a balanced Robertsonian translocation of material between chromosome 13 and 14. A Robertsonian translocation results when the long arms of two acrocentric chromosomes fuse at the centromere and the two short arms are lost. In this case, the long arms of chromosomes 13 and 14 have fused, but no genetic material was lost - this person is completely normal despite the translocation. Common Robertsonian translocations are confined to the acrocentric chromosomes 13, 14, 15, 21 and 22, because the short arms of these chromosomes contain no essential genetic material.

Although people with these translocations have only 45 chromosomes in each of their cells, all essential genetic material is present, and they appear normal. Their children, however, may either be normal and carry the fusion chromosome, or they may inherit a missing or extra long arm of an acrocentric chromosome. The distribution of a Robertsonian translocation chromosome at meiosis can cause serious medical problems or no problems at all!