[Advances in Genetics] Volume 12 || The Biological Coding Problems**Publication 592 from the Division of Basic Health Sciences. The main body of the review is based on literature and other communications received by mid-January 1963. The Addendum is based on later papers received by mid-August.††Abbrevations: mRNA = messenger RNA. sRNA = soluble (adaptor) RNA. Hb = hemoglobin. TMV = tobacco mosaic virus. A, C, G, U, T = adenine, cytosine, guanine, uracil, thymine, respectively, or the corresponding nucleosides and nucleotides. I = inosinic acid (used twice). Forms such as ApUpUp show nucleoside units linked by 3′,5′-phosphodiester groups. Other abbreviations are defined in context.