DNA
DNA (for DesoxyriboNucleic Acid) is a substance, contained in the nucleus of a cell, that bears the genetic information.
Each living being starts as a mere cell, but yet "knows" how to develop itself : it is because its parents left him "schemes" of how to "build" itself : this is the genetic information.
The DNA is a great (really great: it can reach up to 4 cm, about 10,000 times bigger than the cell that contains it!) molecule that encodes the genetic information. It is so big that it wouldn't enter in such a tiny cell : it has to be wind on itself, to make kind of "spool" called chromosome.
The DNA is made of a succession of four different kinds of molecules, the nucleotides. The four different nucleotides are A, T, C and G. They are put one after another so that the order can "write" an information, just as you put letters one after another to write words, or digits one after another to write numbers. The whole genetic information is written this way. A piece of genetic information is called a gene.
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