Genes in prоkаryоtic cells аre frequently pоlycistronic. This meаns that neighboring genes are transcribed into one long mRNA that contains multiple open reading frames (ORF), each of which gets translated into a protein. A commonly used example of such a polycistronic transcription unit is the lac operon in Escherichia coli. The structural genes of the operon (lacZ, lacA, and lacY) are expressed from the same RNA. The respective proteins, β-galactosidase, permease, and transacetylase, contain a total of 494 peptide bonds. There are 3,900 hydrogen bonds in the structural genes of the operon. Calculate: the number of phosphodiester bonds in the mRNA, the % composition of the structural genes in each nucleotide, and the number of nucleotides in the anticodons of the tRNAs that are going to be used during the translation of the peptides. Note: disregard the 5'- and 3'-untranslated regions in the gene and the mRNA, as well as the transcription termination sequence of the operon. If needed, you can use the 'Insert > Equation' menu to enter math equations.