How does DNA work?
DNA is an ideal molecule to transfer genetic messages to every cell of your body. When an egg and sperm met to form the first cell that was to become you, you were given the complete genetic code that all of your cells will use for rest of your life.
In that first cell, half of the chromosomes (half of the DNA molecules) came from your father and the other half came from your mother.
That first cell divided to become two cells, these both divided to become four, then eight then 16 and so on. Some of the cells in your body are still dividing, for example to produce new skin or blood cells. Most of the time a cell divides perfectly and each of the DNA molecules is copied exactly, with one copy going to each of the new cells. If mistakes are made, they are fixed, or the cell marked for destruction.
If a problem occurs in this process the new cells often die, but on rare occasions the faulty cells survive and can cause a wide range of problems. However, sometimes these faults (mutations) can be beneficial for the organism: this is the basis for evolution.
In order to make a copy of itself the DNA molecule unzips lengthwise leaving unpaired bases along each backbone. In the cell there are nucleotides available which are made up of a sugar, a phosphate and one of the four bases. Because A can only pair with T and G can only pair with C, the nucleotides match up with the unpaired bases along the DNA backbone and, like building blocks, form a new strand that is complementary (a match) to the sequence. This forms strands identical to the original strand before it unzipped.
Did you know that several teams of scientists are trying to make a new form of living being from non-living chemicals? They will need to find this new Los Alamos Bug the equivalent of a cell wall and make sure it can metabolise and reproduce itself. The Bug will use a completely different way to hold genetic instructions than DNA – currently scientists are looking to use a molecule called peptide nucleic acid (PNA). Like DNA, PNA is made up of two strands containing the nucleotides A, T, G and C which complement each other, but the molecule itself is soluble in fat instead of water.
Watch how DNA copies itself.
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