An extraterrestrial organism (ET) is discovered whose basic cellbiology seems pretty much the same as that of
terrestrial organisms except that it uses a different genetic codeto translate RNA into protein. You set out to break the
code by translation experiments using RNAs of known sequence andcell-free extracts of ET cells to supply the necessary
protein-synthesizing machinery. In experiments using the RNAsbelow, the following results were obtained when the 20
possible amino acids were added either singly or in differentcombinations of two or three:
RNA 1: 5?-GCGCGCGCGCGCGCGCGCGCGCGCGCGC-3?
RNA 2: 5?-GCCGCCGCCGCCGCCGCCGCCGCCGCCGCC-3?
Using RNA 1, a polypeptide was produced only if alanine and valinewere added to the reaction mixture. Using RNA 2, a polypeptide wasproduced only if leucine and serine and cysteine were added to thereaction mixture. Assuming that protein synthesis can startanywhere on the template, that the ET genetic code isnonoverlapping and linear, and that each codon is the same length(like the terrestrial triplet code), how many nucleotides does anET codon contain?
(a)2 (b)3 (c)4 (d)5 (e)6
An extraterrestrial organism (ET) is discovered whose basic cellbiology seems pretty much the same as that of
terrestrial organisms except that it uses a different genetic codeto translate RNA into protein. You set out to break the
code by translation experiments using RNAs of known sequence andcell-free extracts of ET cells to supply the necessary
protein-synthesizing machinery. In experiments using the RNAsbelow, the following results were obtained when the 20
possible amino acids were added either singly or in differentcombinations of two or three:
RNA 1: 5?-GCGCGCGCGCGCGCGCGCGCGCGCGCGC-3?
RNA 2: 5?-GCCGCCGCCGCCGCCGCCGCCGCCGCCGCC-3?
Using RNA 1, a polypeptide was produced only if alanine and valinewere added to the reaction mixture. Using RNA 2, a polypeptide wasproduced only if leucine and serine and cysteine were added to thereaction mixture. Assuming that protein synthesis can startanywhere on the template, that the ET genetic code isnonoverlapping and linear, and that each codon is the same length(like the terrestrial triplet code), how many nucleotides does anET codon contain?
(a)2 (b)3 (c)4 (d)5 (e)6
