DNA is a type of chemical called a nucleic acid. DNA stands for deoxyribonucleic acid. All of the DNA in your cell, when considered together, is called your genome. Your genome does not consist of one single long DNA molecule, but rather 46 long DNA molecules called chromosomes. You have 23 pairs of chromosomes: one set from your mum and one set from your dad. Along these chromosomes are subunits called genes, which provide a code for making short sections of another type of nucleic acid called RNA. Whereas DNA is a very long-lasting storage molecule which is passed down from generation to generation to generation over millions of years, these RNA molecules are very short-lived templates. RNA is a template for making proteins. Proteins are the building blocks of your cells. For example, one gene will code for an RNA molecule, which will code for a protein such as one of the ‘radial spoke proteins’ which make up part of the cilia in your airways.
Your genome is like a recipe book; with each gene in the genome being like a word in the recipe book. Just as a word in a recipe book tells you which ingredients to mix to make a cake, each gene tells your cells which proteins to make to produce a cilium or other structure in your body.
Just like the words in the recipe book, genes are made up of letters too. Each strand of DNA is formed of four basic building blocks or ‘bases’: adenine (A), cytosine (C), guanine (G) and thymine (T). Sometimes the letters can get swapped, or letters can get added or deleted. This can mean that the code does not make sense anymore, and we make the wrong protein or no protein at all. It is a bit like the letters of your recipe book getting swapped so that you put HAM in the middle of your cake instead of JAM. Just a small 1 letter difference can have a very big effect on how you make your cake. Similarly, just a single letter change in your DNA can have a big impact in how you make a protein, so that your cells and your body work quite differently.