Page about small supernumerary marker chromosomes (sSMC)

The constitutional karyotype of human consists of 46 chromosomes (46,XX or 46,XY).
Each chromosome is present twice, apart from the X- and Y-chromosome in male.
In summary there are 24 different human chromosomes (1-22 and X and Y).

However, about 2.5 million individuals of the whole human population do not have 46 but 47 chromosomes, i.e. 46 normal chromosomes and one small supernumerary marker chromosome (47,XX,+mar or 47,XY,+mar).

These small supernumerary marker chromosomes (= sSMC) can originate from each of the 24 human chromosomes and have different shapes

The group of Dr.  Liehr in Jena, Germany presently characterizes (on request) sSMC from all over the world.
We already characterized sSMC of carriers native from Armenia, Austria, Australia, Belarus, Belgium, Greece, Great Britain, Israel, Korea, New Zealand, Poland, Russian Federation, Spain, Switzerland, Serbia, Slowenia, Taiwan, Turkey, Ukraine, Uruguay, USA and many more.

Moreover, we are setting up a collection of sSMC cases.
For more information go to






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