Central Dogma of Life:

Transcription, Translation and Protein Synthesis

                                                                                                                              Graphic taken from accessexcellence.com                                

The Problem

Proteins are made in the cytoplasm.  DNA is located in the nucleus.  DNA cannot leave the nucleus; it is protected in the nucleus and proteins cannot enter or leave the small pores in the nuclear envelope. 

The Solution

Another nucleic acid, RNA, is able to enter and leave the nucleus at will.  It takes the "recipe" for the needed protein by complementary base pairing with DNA in a process called transcription.  The RNA is getting the message encoded in the DNA but is carrying it in a different form.  When a cultural anthropologist does an oral interview with a person, he or she will record that interview on tape.  Often, the anthropologist will then listen to the tape and type the interview to have a hard copy to look at.  This is called transcription too.  The tape and the "transcript" (paper) mean the same thing; they are two different forms of the same information.  This messenger RNA (mRNA) then goes into the cytoplasm to be translated at the ribosome.  Transfer RNA (tRNA) molecules attach to the mRNA.  A tRNA consists of an anticodon to the mRNA's codon and an amino acid.  These strands meet at the ribosome.  The job of the ribosome is to attach the amino acids together in the order presented with peptide bonds.  A string of amino acids held together by peptide bonds is a polypeptide (or protein)!

(Campbell/Reese Biology 6th Ed. Copyright 2002 Pearson Ed. Inc.)

DNA → RNA → Protein