<prompt> Not true among the following isMost common cause of Downs syndrome is Maternal meiotic disjunction.Most Common inherited condition causing Intellectual disability in Fragile X SyndromeThe mandible in Downs child is smaller than usualIsolated finding of simian crease in Downs in seen in almost 20 of Downs children.  <response>: Isolated finding of simian crease in Downs in seen in almost 1 of Downs children. So it is not a significant finding in a Downs child. 