C.8.3

Outline the role of DNA as a repository of genetics information, including the triplet code.
When cells divide during growth the genetic information has to be replicated intact. This genetic information is condensed and stored in **chromosomes**, found in the nucleus. Chromosomes are effectively a very long DNA sequence. In humans, there are 23 pairs of chromosomes. DNA is unzipped as hydrogen bonds between the bases are being broken, sugar base units will be be picked up from the aqueous solution to form a complementary new strand, which is identical to the original, will be formed. Nitrogenous base adenosine (A) can only bond with base thymine (T), and base cytosil (C) can only bond with base guanine (G). This is the reason the new strand is identical to the original. Figure1. Replication of DNA The coded information held by the DNA lies in the sequence of bases. Each sequence of three bases codes for __one__ amino acid, and is known as the **triplet code**. The triplet code allows for up to 64 permutations known as **codons**. Consecutive DNA codons will transcribe to RNA codons which will cause part of a strand of a protein to be formed that contains the amino acid residues.

Figure 2. Codon Figure 3: The genetic code carried by RNA