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Genes, Chromosomes and DNA: A Quick Guide

It might be hard to believe, but every human being stores a vast quantity of information, just like a computer hard drive or USB memory stick. In fact, it’s been calculated that within us we have enough information to fill up 1.5 GB of storage space – that’s about the storage capacity of 2 CDs or a small memory card like the kind you might have in your camera or phone!

Fair enough, we’re not the most efficient storage for data available, but it’s remarkable nonetheless that every cell of our body contains this huge amount of information encoded in a long chain of molecules called DNA. This information, like computer code, contains all the instructions and data required to create us and keep us running.

Genetics can be a difficult subject to understand, so it helps to start from the very bottom. DNA, which stands for deoxyribonucleic acid, is simply a type of chemical that forms very long molecules. It’s shaped like a ladder, where the rungs are made up of various chemicals – adenine, thymine, cytosine and guanine – that form an alphabet of sorts abbreviated to A, T, C, and G. The actual chemical makeup of these four letter is not important – what is important is the order of the letters in this alphabet.

This alphabet creates “words”, which are stored in “chapters” – the 25,000 or so genes that contain sets of instructions used throughout the body to make proteins. These proteins in turn determine almost every physical characteristic of the human body – including hair and skin colour, the shape of our noses, and more significant effects such as a predisposition to certain diseases. For example, people with brown eyes have a version of a certain gene that is coded to create dark pigment in the iris of the eye. People with blue eyes have the same gene, but in a different version that doesn’t create that dark pigment – resulting in light eyes that appear blue. Chromosomes are simply the “books” that contain these “chapters” – there are 23 in each cell of the human body.

In recent years it’s become easier than ever to find out what your own DNA contains. DNA testing, once an expensive and labour-intensive process, is now more economical and efficient while delivering much improved results. Genetic laboratories can even provide genetic testing kits that can be used at home and returned for analysis by post. In the future, many experts believe that genetic testing will become increasingly common for individuals, helping us to learn more about the code driven deep within our very cells.

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