Contains the full lesson along with a supporting toolkit, including teachers’ notes.
What is DNA?
Deoxyribonucleic acid is better known by its shorter name DNA. The determination of DNA’s structure in 1953 by Francis Crick and Jim Watson is hailed by many to be the most important discovery ever in human history.
DNA is life’s hereditary material, i.e. it holds and passes on the genetic information from parents to offspring. The information carried by DNA directs the construction of each organism, its maintenance, proper functioning and reproduction.
The information is carried in coded form as sequence of specific chemicals called nitrogenous bases. Just as a computer code is a unique sequence of 0s and 1s, so is life’s genetic code a unique sequence of bases.
There are about 2.5 metres of DNA in the nuclear DNA of each human cell. Therefore, we each have about 250 billion kilometres of DNA in our body. Every second we make enough DNA to encircle the equator 3 times. We make about 50 million new cells every second.
What is the structure of DNA?
DNA structure is described as a double helix. It is like a spiral ladder and is composed of two complementary polynucleotide strands held together by hydrogen bonds.
In DNA the sugar is deoxyribose and because there are four different bases – adenine (A), guanine (G), thymine (T) and cytosine (C) - there are four different nucleotides. The nucleotides are PSA, PSG, PST, PSC.