<Tr> <Td> TAA </Td> <Td> UAA </Td> <Td_colspan="3"> Tyr (Y) </Td> <Td> Ter (*) </Td> <Td> </Td> </Tr> <Tr> <Td> TGA </Td> <Td> UGA </Td> <Td_colspan="3"> Trp (W) </Td> <Td> Ter (*) </Td> <Td> </Td> </Tr> <Tr> <Td> Blepharisma nuclear </Td> <Td> 15 </Td> <Td> TAG </Td> <Td> UAG </Td> <Td_colspan="3"> Gln (Q) </Td> <Td> Ter (*) </Td> <Td> As of Nov. 18, 2016: absent from the NCBI update . </Td> </Tr> <Tr> <Td> Chlorophycean mitochondrial </Td> <Td> 16 </Td> <Td> TAG </Td> <Td> UAG </Td> <Td_colspan="3"> Leu (L) </Td> <Td> Ter (*) </Td> <Td> </Td> </Tr>

What is a codon and what is its function