1. Down syndrome is usually caused by an error in cell division called “nondisjunction.” Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.
2. DNA contains the sugar deoxyribose, while RNA contains the sugar ribose.
DNA is a double-stranded molecule, while RNA is a single-stranded molecule.
Choose either one ^^^
Hope this helps you.
