Down Synrdome Karyotype


trisomy-21 karyotype


This karyotype is an example of Down Syndrome (trisomy 21), the most common numerical abnormality found in newborns. It is characterized by an extra chromosome 21 and the karyotype is written as:  47,XY,+21. The key to the karyotype description is as follows:
  • 47:  the total number of chromosomes (46 is normal).

  • XY:  the sex chromosomes (male).

  • +21:  designates the extra chromosome as a 21.



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