Unfortunately all of the pictures that I found including uracil weren't very good and I could hardly read the names. So how do nucleotides "build" DNA? Research done by Chargaff proved that there are equal amounts of adenine and thymine and equal amounts of cytosine and guanine. Watson and Crick later elucidated that adenine hydrogen bonds with thymine and guanine hydrogen bonds with cytosine to create a double helix structure. There are three hydrogen bonds formed between G and C, but only two hydrogen bonds between A and T, making them the weaker pair.
Nucleotides also serve another very important function: when translating RNA into a protein a set of three nucleotides will code for an amino acid. This is called the genetic code. It is said to be mostly universal and degenerate. What is degenerate? When I first heard it I thought it sounded like something terrible, but all it actually means is that one amino acid has many codons (a triplet of nucleotides that codes for an amino acid).
Answer to Saturday's question: Gregor Mendel was actually thought to be crazy back in his time. Nobody believed his results and he was considered a fraud. The leading theory of inheritance in Mendel's day was a blending theory. Scientists thought that both parent's traits mixed together and their offspring was a blend of them all.
Do you know what the difference is between a nucleotide and a nucleoside?