Now scientists from Stanford University and the University of Wisconsin-Madison have solved part of puzzle. Writing in the June 16 edition of the journal Cell, the research team found that a molecule of RNAP makes frequent pauses at specific sites along the DNA double helix. This finding comes on the heels of the team's 2003 discovery that RNAP enzymes routinely make thousands of brief stops ("ubiquitous pauses") when carrying out the vital task of transcribing genetic information from DNA to RNA--a process called transcription.
"Transcription of genes is terribly important," said study co-author Steven M. Block, professor of biological sciences and of applied physics at Stanford. "It's what determines the difference between the cells in your brain or your heart or your liver. All of your cells have exactly the same DNA, but what makes them different is that they transcribe different genes that code for different proteins."
From DNA to RNA to protein
Protein synthesis is strikingly similar in all organisms. It starts with DNA--the famous ladder-shaped double helix, whose rungs (or "bases") consist of four chemical units known by the abbreviations A, T, G and C. A typical DNA molecule contains thousands of genes that encode thousands of proteins, which are essential for life. Each gene consists of a set of DNA bases arranged in a unique sequence that carries explicit instructions for building a specific protein. But one misplaced letter in that sequence--a T substituted for a C, for example--could produce a damaged