FoundationalConceptsNeuroscience

RNA, and where there is an Ain DNA, there would be a T in RNA. How-
ever, for structural reasons thymine (T) does not occur in RNA and is
replaced by the very similar nucleotide molecule uracil, denoted by U.
Thus, the RNA molecule so formed is a copy of the exact genetic infor-
mation in the DNA, but now represented in a slightly different form.
This process is called gene transcription, because transcription means
to make a copy.
The RNA molecule then moves from the cell nucleus to regions of
the cell where synthesis of proteins takes place. Because this RNA car-
ries the genetic message from the DNA to the site of protein synthesis,
it is called messenger RNA, or mRNA. The synthesis of proteins takes
place in structures called ribosomes. In the ribosomes molecules of
transfer RNA match nucleotide triplets in mRNA with their corre-
sponding amino acids, according to the genetic code. The amino acids
are then enzymatically joined into a linear chain by way of peptide
bonds—a protein is born. This process is called gene translation, con-
verting the nucleotide sequence information in the DNA and RNA into
a different form—the sequence of amino acids in a protein.