Masha Gessen has chosen a shrewd title for her book. It simultaneously invokes the old language of blood, family, kinship and biological connectedness, and the new language of genetics in which the formidable power of DNA sequencing intensifies our understanding of what it means to face a serious and life-threatening risk. Blood, in the old sense of being the daughter of a mother who died at 41 from breast cancer, runs alongside the awareness of a 21st-century woman who knows that a genetic test might tell whether her own life is at risk. Does she want to know? And are there effective therapies? Can her embodied identity as a woman cope with radical mastectomy?
Her international journey through genetics laboratories is one of questioning, double checking the predictive power of the genetic diagnosis advice, trying to weigh up the choices of doing nothing while keeping her body under close surveillance, or having the double mastectomy and/or the removal of her womb. There is a chilling moment when the one adviser who does agree that surveillance can be effective expresses strong doubts whether any insurance company would cover treatment. (Hang on to the NHS, dear readers; we may still have to fight postcode care, but it is not our health insurance company that dictates the medical treatment we must have.)
In such tough situations we all have to find how to make such a decision. What works for Gessen - but, I would guess, not for many - is an econometric model of risk and value of life constructed by an economist with her input. For Gessen this confirms the advice of the clinicians, and she opts for a double mastectomy.
One regret is that she has not explored the increasingly rich social science literature in the same way that she covers genetics; this would have enabled her to compare her experience and her decision-making with those of many others. And in the process she would have enriched her book.
Thus in some ways the book belongs to the genre of cancer narratives of those who have fought and survived, and those who have fought and lost. While these are often intensely moving to read, what makes Gessen's book different is that she has used her considerable research skills as a journalist to set out what human genetics can and can't do. Early on she discusses the increased probability of risk through her own ethnic identity as an Ashkenazi Jew. She reports the horror of friends at the DNA re-racialisation of the Jews. She visits Israel, where she finds that the connections between genealogy, genetics and Jewish identity inspire little anxiety. Then, just when she seems to be embracing this all too uncritically, she pauses and reflects. It is precisely this quality of thoughtful reflection that distinguishes the book. Only in her extended account of the country doctor who saves Mormon children whose inbreeding has led to crippling or lethal genetic disorders does her gentle scepticism weaken. It is not that she doesn't mention the setbacks and the partial recoveries, but the hope is strong - and who with any feeling for such children and their families wouldn't hope?
It's true that over-egging the potential health benefits of genetic research has been a constant problem, from the launch of the human genome project and the unqualified claims of what gene therapy could do: solve cancer, heart disease, even homelessness. (Some may find this last suggestion rather hard to believe; it was not made by a tabloid newspaper, but by an editorial in the leading US journal Science.)
The arrival of stem cell research, with its promise to innovate regenerative medicine, has led to a new wave of hope. But after the relatively modest successes of gene therapy derived from the human genome project, it would probably be wisest to blend this hope with a strong dose of caution. Gessen's unsparing account of people with Huntington's disease demonstrates the gulf that lies between DNA disease diagnostics and the delivery of any effective gene, or any other, therapy. It is now 20 years since the much-celebrated isolation of the sequences through which Huntington's is transmitted, but still there is no effective therapy in sight.
However, Gessen ends on a note of hope, telling how a friend with two children with a lethal genetic disorder learned that a designer baby/saviour sibling might save them. Neither she nor the mother felt any ethical qualms. While I find myself profoundly troubled by the ethics of using a baby as means, not as an end, in all honesty I don't actually know what I would have done if I had been faced with such a situation. These are new ethical problems, and the people who confront them are, as the anthropologist Rayna Rapp observes, "moral pioneers".
• Hilary Rose is editor, with Steven Rose, of Alas Poor Darwin: Arguments Against Evolutionary Psychology (Vintage).
