How to Code a Human

14 August 2017
Posted by Kat Arney.

Naked Scientist Kat Arney has a new book out! How to Code a Human is a kind of field guide to genetics, packed with useful diagrams and pictures, explaining how our genes make us who we are. Here’s the introduction:

"It is obvious from looking at any family that people who are closely related tend to appear similar. None of us is a perfect clone of a mother or father, though, and there are even differences between identical twins. Scientists have puzzled over this for thousands of years, devising all kinds of explanations for how traits and characteristics are inherited from our parents. However, it is only in the last century that we have discovered how this information passes down the generations in the form of genes, written in our DNA. It has also become clear that the path from genes to person – or from genotype (genes responsible for a particular characteristic) to phenotype (the physical manifestation of inherited traits) – is not a straightforward one.

To elaborate further, an adult body consists of millions upon millions of tiny cells – nearly 40 trillion according to some estimates – forming organs and tissues with distinct characteristics, shapes and functions. There are hundreds of different cell types, ranging from lung, liver and lymph nodes to bowel, bladder and brain. Yet they all come from one single cell, which is created when a sperm fertilises an egg. This cell divides in half, creating two cells. These grow and divide again to make for cells that, in turn, divide again and again. Over time, cells in different parts of the growing embryo begin to specialise, eventually creating all the various types of cells needed to make a baby. However, this process does not stop there. As the human body develops further, cells continue to divide constantly, replacing damaged and worn out cells and preparing wounds.

We now know that genes control all these processes and also respond to the environment around them – nature and nurture of therefore both very important. Scientists are only just beginning to find the answers to some really big questions such as:

  • How does a fertilised egg divide and specialise to make all the tissues of the body?
  • Why does a liver cells stay in the liver and a brain cell remain in the brain?
  • How do genes make you the person you are?
  • How are traits, characteristics and diseases inherited?

During the 1960s, scientist started to piece together the concept of the molecular gene, discovering that genes are stretches of DNA encoding specific instructions telling cells to do something (usually to make a specific molecule, such as protein).  Around the same time, computers were becoming more sophisticated, so it was easy to make comparisons between the strings of chemical “letters” that make up DNA and the logical string of digits or commands within computer code. Following on from this was the idea that if we could just crack the code and read all our genes, then we would understand exactly how our cells and bodies work.

Over the past few decades, it has become clear that this view is far too simplistic. Instead of being a computer code, with tidy electric circuits, genes are more like recipes. They are living entities, full of constantly shifting molecules and with many options for flexibility, depending on the range of things a cell needs to manufacture. Somehow, in the midst of all this biological hurly-burly, genes need to be switched on and off at the right time and in the right place to ensure that cells continue to function properly.

It is also important to note that there is no such thing as a gene "for" a trait, such as height or intelligence, or "for" a disease, like cancer. Genes are recipes for making molecules, and it’s how all these molecules work together in our cells, body and brain – along with the environment around us – that make us who we are and determines our risk of all kinds of illnesses.

We will look closely at the human genome, discovering how genes work and the way in which the twisted double helix of DNA encodes the instructions for life. We will track the journey made by our genetic ancestors out of Africa and around the planet and see what traces of them remain in our genes. We will find out how our DNA makes us who we are, right from the very beginning when the egg and sperm meet, and how cells remember what they are supposed to be doing. We will uncover the genes that shape our bodies and build our brains, and discover what happens when things fail to work as they should. Finally, we will look at what the future might hold, for both our genes and the entire human species.”

Kat's first book, Herding Hemingway’s Cats: Understanding how our genes work is also available in paperback, audiobook and Kindle versions from all retailers - it’s a more in-depth look at the latest ideas in genetics, with personal interviews with experts on the cutting-edge of the field.

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