Artificial RNA molecules of a single sequence, i.e., UUU, were added to a mixture of RNA and protein from ruptured cells, and scientists observed the type of protein that resulted. Only one codon at a time is receptive to a tRNA anticodon on the ribosome, and tRNA anticodons are specific for both the codons to which they bind and the amino acids they carry. Translation is initiated through the formation of an initiation complex. Through elongation factors and translocation, the protein grows in length as the ribosome moves down the mRNA chain. Elongation factors assist in the binding of the tRNA to the appropriate mRNA codon.
Exons are the segments of DNA that actually code for the production of a specific protein.
Both introns and exons are transcribed into mRNA, but prior to leaving the nucleus, the introns are processed out of the so-called primary transcript, leaving only exons in the stretch of mRNA leaving the nucleus.