What are the chromosomal aberrations of Down syndrome?

Trisomy 21: This is the most common chromosomal aberration associated with Down syndrome. It occurs when there are three copies of chromosome 21 instead of the usual two. This extra copy of chromosome 21 leads to the characteristic physical and mental features of Down syndrome.

Translocation Down syndrome: This occurs when a piece of chromosome 21 breaks off and attaches to another chromosome, usually chromosome 14 or 22. This results in three copies of the 21q region, which contains the genes responsible for Down syndrome.

Mosaic Down syndrome: This is a rare form of Down syndrome in which only some of the cells in the body have an extra copy of chromosome 21. This can lead to a milder phenotype, as not all of the cells are affected by the extra chromosome.