Reverse translation of protein sequence into nucleic acid sequence. The Genetic Code is degenerate so there may be several possible nucleic sequences: the five amino acids shown in the example can be reverse translated into 16 possible nucleic acid sequences. All 16 sequences can be synthesized at the same time to make a collection of all the oligonucleotides ("degenerate" oligonucleotides). These oligonucleotides can be used as a probe if labeled with radioactive phosphate using T4 polynucleotide kinase.