Using computer animation based on molecular research, we are now able to
see how DNA is actually copied in living cells.
You're looking at an assembly line of amazing miniature biochemical machines
that are pulling apart the DNA double helix and cranking out a copy of each
strand.
The DNA to be copied enters the production line from the bottom left.
The whirling blue molecular machine is called helicase.
It spins the DNA as fast as a jet engine
as it unwinds the double helix into two strands. One stand is copied continuously
and can be seen spooling off to the right.
Things are not so simple for the other strand
because it must be copied backwards.
It is drawn out repeatedly in loops and copied one section at a time. The end
result is two new DNA molecules.