DNA (deoxyribonucleic acid) is the primary genetic material in all
living organisms - a molecule composed of two complementary strands that
are wound around each other in a double helix formation. The strands are
connected by base pairs that look like rungs in a ladder. Each base will
pair with only one other: adenine (A) pairs with thymine (T), guanine (G)
pairs with cytosine (C). The sequence of each single strand can therefore
be deduced by the identity of its partner.
Genes are sections of DNA that code for a defined biochemical function, usually the production of a protein. The DNA of an organism may contain anywhere from a dozen genes, as in a virus, to tens of thousands of genes in higher organisms like humans. The structure of a protein determines its function. The sequence of bases in a given gene determines the structure of a protein. Thus the genetic code determines what proteins an organism can make and what those proteins can do. It is estimated that only 1-3% of the DNA in our cells codes for genes; the rest may be used as a decoy to absorb mutations that could otherwise damage vital genes.
mRNA (Messenger RNA) is used to relay information from a gene to the protein synthesis machinery in cells. mRNA is made by copying the sequence of a gene, with one subtle difference: thymine (T) in DNA is substituted by uracil (U) in mRNA. This allows cells to differentiate mRNA from DNA so that mRNA can be selectively degraded without destroying DNA. The DNA-o-gram generator simplifies this step by taking mRNA out of the equation.
The genetic code is the language used by living cells to convert information found in DNA into information needed to make proteins. A protein's structure, and therefore function, is determined by the sequence of amino acid subunits. The amino acid sequence of a protein is determined by the sequence of the gene encoding that protein. The "words" of the genetic code are called codons. Each codon consists of three adjacent bases in an mRNA molecule. Using combinations of A, U, C and G, there can be sixty four different three-base codons. There are only twenty amino acids that need to be coded for by these sixty four codons. This excess of codons is known as the redundancy of the genetic code. By allowing more than one codon to specify each amino acid, mutations can occur in the sequence of a gene without affecting the resulting protein.
