Everything about us starts with our DNA.
Your DNA is like your thumbprint. It is yours and yours alone. Unless you have an identical twin, no one else on the planet has exactly the same DNA as you.
So what is DNA?
Very simply, DNA is the substance which carries the code or language of the body's instruction manual. Our bodies are made up of millions of cells, and in the centre (nucleus) of each cell are 23 sets of chromosomes, 46 in total, that are called your genome. In each chromosome the DNA is organised into genes. Your genome contains about 30,000 genes. Each gene carries information that enables the cell to perform a particular task,
How does something so small contain all of the instructions to make your whole body and keep it working? That is answered in the chemical makeup of DNA. If you think of your genome (all of your chromosomes) as the book that makes you, then the genes are the words that make up the story. They do that by making proteins, which do most of the real work in the body. The DNA in your genes tells the cell what amino acids (protein building blocks) to put together to make a protein. The letters that make up the words are called DNA bases, and there are only four of them: adenine(A), guanine(G), cytosine(C), and thymine(T).It's hard to believe that an alphabet with only four letters can make something as wonderful and complex as a person!
There are several insights that help us appreciate how this happens.
One insight is the vast number of different arrangements possible with several billion letters in the genome, even if there is a choice of only four possibilities for each "letter".
Another insight is Darwin's understanding of the role of natural selection in shaping the choice between the different possibilities. But there is still a huge amount that is not well understood – such as whether, when or how the cell comes to make use of any particular instruction. All the instructions used anywhere in the body are present everywhere – so we need to know more to explain how different cell types come to specialise in the ways that they do.
We cannot answer all the questions you might have, but to understand more about genetics, inheritance patterns and how things can and do go wrong please follow the sections listed in the left-hand panel.