Guest Post by Nicola Davies
My new book Grow: Secrets Of Our DNA, illustrated so beautifully by Emily Sutton, aims to open the world of genes to young readers and their grown-ups. But what do you think of when you hear the word ‘gene’? Maybe you think of GM ‘genetically modified’ crops; or of gene therapy for congenital diseases; or maybe you vaguely remember something about a monk and some pea seeds, from biology class in school. You probably think of test tubes and scientists in white lab coats. But genes are much closer to home than that, and knowing about them can help answer questions that children may ask like, ‘Why are animals and plants different from us?’ ‘How do I grow ?’ and ‘ How did I grow from a tiny blob in mum’s tummy?’
The answer is genes. Because genes are in essence are a set of instructions for building bodies. They are written in a chemical code, formed by the endless variations in the way four different components of one chemical compound, deoxy ribonucleic acid, DNA, can be strung together. And different sets of genes build different sorts of bodies.
It takes about 20,000 genes to list the complete instructions for building a human body, including genes to switch one gene off and turn another on, genes to slow some processes down and speed others up. Genes don’t just shape the ‘what’ of bodies’ but the ‘how’ and ‘when’ too. For example if you look at the shape of a human new born, it’s all head, but the legs and arms are tiny. That’s because human babies can rely on being carried about after birth so it makes sense for the heads to grow and their legs can catch up later. A new born zebra however is obviously very ‘leggy’ because from birth the most important thing for a zebra to do is run.
Genes don’t just stop working at birth or when you reach maturity, they are at work all the time, governing the maintenance, running, and repair of every bit of you. Almost every single cell of your body has your unique version of DNA in it, a double stranded string almost two meters long, packed into a space far too small to see with the naked eye.
TV crime dramas encourage us to think of each person’s DNA being absolutely unique to them. It’s true that some of your DNA is not like anyone else’s, but quite a bit of it is just like the DNA in a fish or even a pot plant. That’s because some of the basic features of your body, such as how your cells produce energy, are the same in most living things. These basic features evolved a really long time ago and the instructions for how to do them haven’t really changed, and have been passed down the millions of generations of living things. The DNA coding for more advanced features, such as your hands or the way your brain is put together, is unique to you although very similar to that of other human beings.
DNA has many stories to tell us, about the long history of life on earth, and when and how the enormous variety of different living things alive today, and in the past, evolved. It can even tell us something about the history of our own species or even our own human families. But perhaps the most important message carried in our DNA is that all life on earth is related, and that all our stories, whatever race, whatever nation or species to which we belong are written in the same language.
Grow: Secrets of our DNA publishes on 2nd April 2020 by Walker Books.