Chapter 8, Problem 11P

Before the technology existed to synthesize RNA molecules of defined sequence like those in Fig. 8.5 (p. 260), similar experiments were performed with synthetic mRNAs of undefined sequence. For example, RNAs consisting only of Us and Gs could be synthesized in vitro, but they would have random sequences. Suppose a pool of random sequence RNAs was synthesized in a reaction mixture containing three times as much UTP as GTP, and that the resulting RNAs were translated in vitro.

a.	How many different codons exist in the RNAs?
b.	How many different amino acids would you find in the polypeptides synthesized?
c.	Why are your answers to (a) and (b) not the same?
d.	How frequently would you expect to find each of the codons in (a)?
e.	In what proportions would you expect to find each of the amino acids in the polypeptides?
f.	If you did this experiment—that is, synthesized random-sequence RNAs containing a 3:1 ratio of U:G, and quantified the amount of each amino acid in the polypeptides produced—prior to knowledge of the genetic code table, what would the results have told you?