Is down syndrome homozygous or heterozygous?

Answer 1

Diabetes mellitus is represented by 'D' for dominant trait i.e. person is normal or not suffering from diabetes.Diabetes mellitus is a homozygous recessive trait i.e. 'dd'. A person having this trait will suffer from diabetes.

Answer 2

It is not determined by a genotype, but has to do with the number of chromosomes the individual has. A person with down syndrome has 47 chromosomes, instead of 46 (an extra copy of chromosome 21).

Answer 3

NO; Monosomy indicates that there is ONLY one chromosome, one from mom or from dad (the second chromosome form mom or dad is missing. Humans should have set of two inherited chromosomes, one from each parent. (In normal healthy individuals, there are a set of two of each chromosome in the body, one from each parent.)

With Down syndrome, it is a condition caused by trisomy, in which a chromosome (in this case chromosome 21) is replicated, resulting in three copies of the chromosome, one extra; the normal two, plus a copy.