Country: United States Date: May 2007 I understand than when a
dna-polymerase is making a copy of a dna strand, it attaches
nucleosides that are present in it´s surroundings, but how does
the enzyme "picks" or "catches" the nucleosides in order to
attach them to the template strand if they are somehow "floating
around" randomly? First, the nucleotides are nearby. They are
floating around, and thanks to the natural vibrations of
molecules (Brownian motion), they move back and forth and bump
into the polymerase continuously. The way nucleotides attach has
to do with the shape of the DNA polymerase and the shape of the
nucleotide (here, they're nucleoTides, not nucleoSides). As you
may know, enzymes (DNA polymerase being one kind of enzyme) have
very specific, special shapes to allow their target molecules to
attach, or 'bind', to them. Not only the shape, but also the
chemistry of the enzyme -- sometimes people use a lock-and-key
analogy, but that's not the whole story; it's more like a lock
that changes shape