Live at the Improv: DNA Polymerase
When a DNA reader hits an unfamiliar line, it improvises, reports EurekAlert:
Prof. Zvi Livneh and Ph.D. student Ayelet Maor-Shoshani of the Biological Chemistry Department cut a DNA strand — from the bacterium E. coli — and inserted material similar to that which composes crude oil in between both its ends. As expected, the regular DNA polymerase stopped working when it reached the foreign material. Yet to the scientists’ amazement, a specialized DNA polymerase jumped in to rescue the stalled replication process, and continued the copying process, inserting nonexistent genetic components into the “printout’ when it encountered the foreign material. This can be compared to a person who forgets some words in a song and makes up new ones to be able to continue to sing.
The scientists believe this capability provides resilience against damaged DNA, except in the most extreme cases:
True, when DNA polymerase improvises a tune, errors (i.e. mutations) may occur in the new cells’ DNA. Yet Livneh explains that the body cannot feasibly let all cells with damaged DNA die, for there are too many of them. “Only if the DNA contains a very high level of damage will the cell’s machinery ‘give up’ and let the cell die.”
The number of coded mechanisms keeping us alive is astonishing. Given all the things that could go wrong, it makes you wonder how the human race survives for even a few generations, let alone thousands of years. Molecular machines in the cell are multi-talented and well trained, and now even skilled at improvisation. Be thankful your gene readers know all that jazz.