Describe the nature of the genetic code

Genes are regions of DNA that code for proteins. They are transcribed into mRNA and translated into proteins at the ribosome. Genes are formed of nucleotides, or the bases that are found in DNA (Adenine, A, Cytosine, C, Guanine, G and Thymine, T, and Uracil, U in RNA). The order of the nucleotides in a gene is known as its sequence. Every three nucleotides are known as a codon, and each codon is specific to a particular amino acid (the building blocks of proteins), or to a STOP codon, which stops transcription and translation when the full protein has been made. The genetic code is highly conserved and the same nucleotides are transcribed and translated in prokaryotes (bacteria) and eukaryotes (plants, animals). Genes are always transcribed in the same direction, from the 5' C end of a molecule of DNA to the 3' C end.
There are 20 amino acids that form parts of proteins in the cells and in the body. If every two nucleotides formed a codon for an amino acid, there would be too few combinations of the four nucleotides to encode every amino acid (because 4 to the power of 2 is 16). Therefore, since there are three bases in a codon (and 4^3 = 64), there are 64 possible combinations of nucleotides in a codon. Because of this, multiple codons can code for the same amino acid; the genetic code is degenerate. Furthermore, a genetic sequence is only read in one way, meaning that only by starting at a certain point or nucleotide on a gene can the protein be sequenced correctly; a single nucleotide cannot form parts of multiple codons, and genetic sequences are highly specific to the proteins that they encode. The three codons that do not encode amino acids are UAA, UGA and UAG; instead, they are called STOP codons and when they are read, transcription and translation terminates.