RNA is single-stranded while DNA is double-stranded. RNA contains uracil while DNA contains thymine. RNA has the sugar ribose while DNA has the sugar deoxyribose.
DNA has four nitrogen bases, one of them being thymine. For RNA, instead of having thymine, it has uracil. DNA is a double stranded (also known as double helix) and RNA is single stranded. This explains why RNA can leave the nucleus and DNA can’t.
