So trisomy 21 is the much more common case of down syndrome. Now, the other much less common form of down syndrome is translocation. Now, translocation, if you remember from our discussion on chromosomal abnormalities, translocation is the process by which a segment of a chromosome breaks off and moves onto and attaches onto a different non Homologous chromosome. So translocation can also lead to down syndrome. But in an individual that has down syndrome due to translocation, that individual actually contains the normal number of chromosomes 46. But one of those chromosomes is actually abnormal.