What is the difference between DNA and mRNA?

DNA and mRNA are both nucleic acids and are made up of a sugar, phosphates and a base. However, they are very different. Firstly by simply looking at the molecules DNA is double stranded whereas mRNA is single stranded. RNA has a ribose sugar and DNA has a deoxyribose sugar: a good way to remember is R = RNA = Ribose and D = DNA = Deoxyribose. DNA has 4 bases that determine the sequence: thymine, adenine, guanine and cytosine. RNA however swaps out thymine for a base called uracil. Therefore, due to their different structures they have different functions!