DNA is like a book of instructions written in the alphabet of A, T, G, and C. However, merely
knowing the letters does not tell us how the genes work.
Two processes called transcription and translation are
required to synthesize proteins. In addition, RNA plays a critical role in the process. The same
two steps produce ALL proteins:
DNA is transcribed to form RNA. This occurs in the nucleus. The RNA moves into cytoplasm. In
transcription, molecules of RNA are produced on the DNA templates in the nucleus.
RNA is translated to form polypeptide chains, which fold to form proteins. In translation, RNA
molecules are shipped from the nucleus to the cytoplasm to be used in polypeptide assembly.
Three Classes of RNA
There are three classes of RNA:
Messenger RNA (mRNA) that carries protein-building instructions or the "blueprint" to the
ribosome.
Ribosomal RNA (rRNA) that combines with proteins to form ribosomes upon which polypeptides are
assembled.
Transfer RNA (tRNA) that brings the correct amino acid to the ribosome and pairs up with an
mRNA code for that amino acid.
REVIEW: DNA contains many different genes that are transcribed into different _____ .
