== Original Research Tag == 

 I've added the tag due to a few lines in the article. First, the WP:LEAD. his exact role in the discovery of Trisomy 21 is considered controversial; see the controversy section below. is not cited. I added a 'citation needed' tag before I renamed my account, but it's been removed, in spite of WP:LEADCITE and WP:MINREF, requiring an inline citation if it is challenged. This has not happened. 

 As well as As of today the Website of the Lejeune foundation describes the discovery as the sole work of Lejeune: "In July 1958, as he was studying chromosomes linked to Down syndrome, he discovered the existence of an additional chromosome on the 21st pair. which is taking a side, contrary to WP:NPOV, among other things contributed to me adding this tag. 

 As well, I've added the 'undue weight' tag to the 'controversy' section due to the source used RenewAmerica.com, per WP:QUESTIONABLE.