Date: Wednesday, 21-June-2017, 11:51 AM | Message # 1
DNA Replication Has Been Filmed For The First Time, And It's Not What We Expected
"It undermines a great deal of what's in the textbooks." BEC CREW 19 JUN 2017
Here's proof of how far we've come in science - in a world-first, researchers have recorded up-close footage of a single DNA molecule replicating itself, and it's raising questions about how we assumed the process played out.
The real-time footage has revealed that this fundamental part of life incorporates an unexpected amount of 'randomness', and it could force a major rethink into how genetic replication occurs without mutations.
"It's a real paradigm shift, and undermines a great deal of what's in the textbooks," says one of the team, Stephen Kowalczykowski from the University of California, Davis.
"It's a different way of thinking about replication that raises new questions."
The DNA double helix consists of two intertwining strands of genetic material made up of four different bases - guanine, thymine, cytosine, and adenine (G, T, C and A).
Replication occurs when an enzyme called helicase unwinds and unzips the double helix into two single strands.
A second enzyme called primase attaches a 'primer' to each of these unravelled strands, and a third enzyme called DNA polymerase attaches at this primer, and adds additional bases to form a whole new double helix.
You can watch that process in the new footage below:
This video shows replication of individual pieces of double stranded DNA. This is the first time individual steps in DNA replication -- arguably, the fundamental process of life on Earth -- have been observed directly.
Each glowing strand is a piece of double helix growing by replication at the left-hand end. They move at different speeds and stop and start. Dark gaps in the line are single-stranded DNA where one polymerase failed to attach (the fluorescent dye only binds double-stranded DNA).
Some surprises come out of being able to observe replication directly. For example, the two polymerases involved in replication (one for each strand) aren't coordinated. They stop and start at random, but overall they move at the same average speed, so everything works out. This stochastic model is quite different from a smooth-running, coordinated machine usually imagined.