Wednesday, May 12, 2010

The Language of Life, by Francis S. Collins

The Language of Life: DNA and the Revolution in Personalized MedicineI was just browsing the New Books section at the library and saw this book, decided it sounded interesting. I wasn't wrong. Collins is the former head of the Human Genome Project, so he's seen the field of genetics explode over the last few decades, providing him with unrivaled insights into the past, present and future of the intersection of genetics and medicine. Given some of his discussions of hemophilia in the book, one could rightfully say he's on the bleeding edge of this technology.

Mundanely enough, Collins says that the single most important source of information about your future health is to be your family health history! "Family health history turns out to be the strongest of all currently measurable risk factors for many common conditions..."

Collins mentions the science fiction film, GATTACA, when he's discussing the potential of newborn genetic screening. Strangely enough, I've never watched that film, and it suddenly dawned on me as I was reading The Language of Life that the title of the film is a genetic code, containing the letters for the four DNA bases, Guanine, Adenine, Cytosine and Thymine. Insert forehead smack here. Interestingly, he says it's estimated that 60 to 70 percent of one's adult body weight is determined by genes, so if a child is born with a predisposition to obesity, parents could adjust the child's diet so as to avoid the all too commonly seen childhood obesity later on.

It's even possible to do a genetic scan earlier than at birth, with a process called PGD (pre-implantation genetic diagnosis). This isn't practical for naturally conceived children, but for parents undergoing IVF (in-vitro fertilization) procedures. At the eight-cell stage of division, it's possible to remove one cell without affection future development of the embryo, and to then perform a genetic scan. Of course, there are ethical questions raised about what we do with this information, but if it was used to inform the parents or the child, itself, of possible future medical issues, rather than as a go/no go decision point to abort the fetus, I don't think most people would have an ethical problem with it, any more than performing an amniocentesis is done today.

There are actually several readily available commercial genetic screening tests at this time, which can scan for some of the most common genetic risk factors. They're a little spendy, but what's it worth to know that you're at a higher risk for a specific disease than the general population and to be able to take preventative steps? Some of the more common diseases for which genetic risk factors are well-identified are heart disease, breast cancer, colon cancer, sickle cell anemia, and diabetes.

Collins describes the three types of genes that have a role in preventing cancer; any of which can pose a cancer risk when they're defective. There are the oncogenes, which code for proteins that normally promote cell growth. The oncogenes' growth signals are ordinarily tightly regulated, occuring only in the right conditions. A mutation in this type of gene, however, can remove the restraints from the growth signal, causing cell growth to go out of control, like a Toyota on the highway. There are also cancer genes called tumor suppressors, whose function, as you might suspect, is to act as a brake on cell growth when it's time for cells to stop growing. One of these genes, called p53, actually stops the process of cell replication if it determines that the DNA in those cells has been damaged. A third type of cancer gene is one that performs like a DNA spell-checker. If there are defects in the genetic code, it will create repair enzymes to fix the code.

Collins says that most of the mutations in a cancer cell are not hereditary, but are acquired during a person's lifetime. Just the error rate in copying 6 billion base pairs of DNA in the 400 trillion cells within the human body causes most of these mutations, without taking into account any envirommental effects. That most of us go through life without being afflicted with cancer is the result of the work of the cancer-preventing genes.

Knowing how these and other genes do their work has proven key in the treatment of a number of diseases. This knowledge has helped doctors and pharmaceutical companies develop drugs that treat the causes of some diseases at a genetic level, or by stimulating production or suppression of proteins that are lacking or in too much abundance. It has helped avoid some adverse drug reactions - what was the figure he used? - there are 100,000 deaths a year in the U.S. alone from adverse drug reactions!

The areas where genetics is a little less sure are that of personality, spirituality, intelligence, and sexuality. In his section on researching the causes of male infidelity, Collins mentions one fun fact you can use to astonish your friends. Among North American voles, "Prairie voles make lifelong monogamous pair bonds, while their close relatives, the montane and meadow voles, do not, indulging instead in a series of one-night stands." So Tiger does have an excuse; he wasn't under his own vole-ition.

In total, this book is fascinating reading for the layperson. Collins does a great job of explaining a horrendously complex subject in simple words and sentences.

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