The first step of replication is "unzipping" the DNA molecule. This will divide
the molecule lengthwise.
Select Unzip to divide the molecule.
Selecting the "Unzip" button causes the DNA molecule to split lengthwise.
What Happened Window:
In a real cell, the molecule unwinds from spools made of protein, then
untwists. (Here the molecule is already unwound and untwisted.) The DNA now
resembles a ladder. Enzymes, special kinds of proteins, move up the ladder,
breaking the rungs.
Drag and drop from well:
DNA is made up of four types of bases: adenine (A), cytosine (C), guanine (G),
and thymine (T). Each base has a complement -- another base that it can connect
to. A complements T, and C complements G.
Drag bases from the left to their complementary bases on the DNA strands. Don't
worry about the orientation of a base -- it will automatically flip, if it
needs to, as it approaches the DNA strand.
Nucleotides are dragged from one area of the screen to the separated DNA strands.
What Happened Window
Well done. Replication is complete.
Our new DNA molecules consist of only a few base pairs. Not so with real DNA.
Each human chromosome, for example, contains millions of base pairs. All 46
human chromosomes contain 3 billion pairs.
If you haven't already done so, check out Protein Synthesis.