To crack the genetic code, researchers introduced synthetic messenger RNAs into in vitro translation systems and determined which proteins were produced from these synthetic mRNAs. mRNAs consisting of poly-UUC led to production of three different proteins: poly-Phe, poly-Ser, and poly-Leu. What best explains this result

To crack the genetic code, researchers introduced synthetic messenger RNAs into in vitrotranslation systems and determined which proteins were produced from these synthetic mRNAs. mRNAs consisting of poly-UUC led to production of three different proteins: poly-Phe, poly-Ser, and poly-Leu. What best explains this result?

A.   Each amino acid is specified by several codons.

B.   Transcription started at three different places.

C.   The synthetic mRNA was read in all three reading frames.

D.   Each codon codes for several different amino acids.

The synthetic mRNA was read in all three reading frames.

Explanation:

Genetic code is universal and is the same for all living beings. The code UUC specifies amino acid phenylalanine while the genetic code UCU codes for the amino acid serine. Similarly, the genetic code CUU codes for leucine. A genetic code is coma-less which means that the nucleotide sequence of mRNA is read continuously.

Formation of poly-Phe, poly-Ser, and poly-Leu from a single mRNA having poly UUC sequence represents the fact that nucleotide triplets were read in all three possible frames which are UUC (phe), UCU (ser) and CUU (Leu).