Help me explain how the complementary base pairing rule allows for an exact replication of the DNA molecule.?

Question

This is biology, i don't understand it.

Answer 1

only one base can pair with another nuclotide, limited chance of mismatching

Answer 2

A=Adenine, T=Thymine, C=Cytosine, G=Guanine are the four nucleotides in DNA (and involved in replication).

In a double-stranded DNA helix, an A can only base pair with a T, a C can only base pair with a G. When the strands separate during replication, the complementary base pairs are no longer bound to each other (via hydrogen bonds). Since the bases are now "open," another complementary nucleotide will bind to the separated strand. This process occurs on each strand, leading to 2 identical double-stranded helices.

It might be easier to draw a diagram, and go through the steps, than just read my post. While this is an overview of base pairing, I haven't gone into the actual process of how new nucleotides are added to each separated strand.

Answer 3

Bases only pair together in certain ways. Each base has its own shape and will only fit together with one other kind of base.

AT go together -- think "these letters are made with straight lines"
CG go together -- think "these letters have curves"

When the DNA molecule is "unzipped" and leaves bases that need new partners, the new partners can only fit into the empty spots if they have the right shape to fit in the "puzzle". This guarantees that the new molecules will be just like the original.