The nucleotide triplet that encodes an amino acid is called a codon. Each group of three nucleotides encodes one amino acid. Since there are 64 combinations of 4 nucleotides taken three at a time and only 20 amino acids, the code is degenerate (more than one codon per amino acid, in most cases).
No, not gastric ulcers. Ulcers, yes. But gastric ulcers are specific to the digestive system, hence the word gastric! :)
