Junk DNA: A Journey Through the Dark Matter of the Genome by Nessa Carey Page B

changing the coat colour of a particular strain of mice – to much more dramatic, such as an increased risk of cancer.
    A major role of junk DNA, only recognised in the main in the last few years, is to regulate gene expression. Sometimes this can have a huge and noticeable effect in an individual. One particular piece of junk DNA is absolutely vital for ensuring healthy gene expression patterns in female animals. Its effects are seen in a whole range of situations. A mundane example is the control of the colour patterns of tortoiseshell cats. At its most extreme, the same mechanism also explains why female identical twins may present with different symptoms of a genetically inherited disease. In some cases, this can be so extreme that one twin is severely affected with a life-threatening disorder while the other is completely healthy.
    Thousands and thousands of regions of junk DNA are suspected to regulate networks of gene expression. They act like the stage directions for the genetic script, but directions of a complexity we could never envisage in the theatre. Forget about ‘Exit,pursued by a bear’. These would be more along the lines of ‘If performing Hamlet in Vancouver and The Tempest in Perth, then put the stress on the fourth syllable of this line of Macbeth . Unless there’s an amateur production of Richard III in Mombasa and it’s raining in Quito.’
    Researchers are only just beginning to unravel the subtleties and interconnections in the vast networks of junk DNA. The field is controversial. At one extreme we have scientists claiming experimental proof is lacking to support sometimes sweeping claims. At the other are those who feel there is a whole generation of scientists (if not more) trapped in an outdated model and unable to see or understand the new world order.
    Part of the problem is that the systems we can use to probe the functions of junk DNA are still relatively underdeveloped. This can sometimes make it hard for researchers to use experimental approaches to test their hypotheses. We have only been working on this for a relatively short space of time. But sometimes we need to remember to step back from the lab bench and the machines that go ping. Experiments surround us every day, because nature and evolution have had billions of years to try out all sorts of changes. Even the brief geological moment that represents the emergence and spread of our own species has been sufficient time to create a greater range of experiments than those of us who wear lab coats could ever dream of testing. Consequently, throughout much of this book we will explore the darkness by using the torch of human genetics.
    There are many ways to begin shining a light on the dark matter of our genome, so let’s start with an odd but unassailable fact to anchor us. Some genetic diseases are caused by mutations in junk DNA, and there is probably no better starting point for our journey into the hidden genomic universe than this.

1. Why Dark Matter Matters
    Sometimes life seems to be cruel in the troubles it piles onto a family. Consider this example. A baby boy was born; let’s call him Daniel. He was strangely floppy at birth, and had trouble breathing unassisted. With intensive medical care Daniel survived and his muscle tone improved, allowing him to breathe unaided and to develop mobility. But as he grew older it became apparent that Daniel had pronounced learning disabilities that would hold him back throughout life.
    His mother Sarah loved Daniel and cared for him every day. As she entered her mid-30s this became more difficult because Sarah developed strange symptoms. Her muscles became very stiff, to the extent that she would have trouble releasing items after grasping them. She had to give up her highly skilled part-time job as a ceramics restorer. Her muscles also began to waste away noticeably. Yet she found ways to cope. But when she was only 42 years old Sarah died suddenly from a cardiac arrhythmia, a