15. A scientist puts nucleotide chains of into a test tube and theen allows protein synthesis to take place. Soon, the test tube is full of polypeptide chains made entirely of the amino acid phenylalanine. What does this experiment indicate? 1. that the amino acid phenylalanine is composed of uracil (U)
2. UUU codes for phenylalnine
3. protein synthesis did not occur
4. all proteins are composed of only one type of amino acid