Iis down syndom caused by a dominant or recessive allele?

Answer 1

Down syndrome is not catagorised as co-dominant or incomplete dominance, its trisomy 21; this means that you have a third or part of a third Chr21, causing the condition.

Answer 2

Neither. Down's Syndrome is cause by there being an extra chromosome included in the egg that gave rise to the individual.

Answer 3

It's neither