In 2004, journalist Masha Gessen learned through genetic tests that she was predisposed to develop breast cancer, which had killed her moth­er in middle age. Faced with choosing whether or not to take preemptive measures, including surgical removal of her ­still-­healthy breasts and ovaries, she embarked on a research bender. The result was a series of personal essays for 

—­which eventually became the frame for 

, an intelligent and imaginatively researched tour of modern ­genetics.

Today, relatively simple tests can reveal patients’ predispositions toward hundreds of ­diseases—­and even diagnose disorders in human embryos before implantation during fertility treatments. With each year the list of detectable genetic diseases grows, as does the number of books about this suddenly common medical experience and its attendant dilemmas. (In last year’s

, for example, Beth Kohl tackled the ethical quandaries of creating “designer” babies through reproductive technology.)

Characterized by Gessen’s publisher as a “field guide,” 

 is more properly described as a collection of dispatches from the field. Her approach seems to draw from her days as a war reporter: She traverses unfamiliar, often risky terrain in search of interesting stories, visiting with scientists, doctors, genetic counselors, religious thinkers, and a host of individuals and families stricken by genetic disease. Jewish communities receive special attention, both because of Gessen’s own Jewish background and because these ­semi­closed groups have been well studied by gene­ticists. A 2005 study, for example, hypothesized that the same genetic mutations that predispose many Jews to diseases such as ­Tay-­Sachs and Gaucher also give them higher ­IQs.

Gessen jumbles the research related to her own genetic ­mutation—­hearings with genetic counselors, doctors, other cancer “previvors,” even an economist who helped her calculate her personal ­risks—­with a series of junkets into the world of genetics. She explores Nazi eugenics, Huntington’s disease, the new use of sci­ence in matchmaking among Jewish families to prevent marriages between genetically “incompatible” individuals, various illnesses prevalent among closed communities such as Old Order Mennonites, and the genetic components of behavior studied in a Russian facility that breeds foxes, minks, and rats of various ­temper­aments.

But it is Gessen’s writing about her own mutation and deftly chosen family anecdotes that possess much of 

narrative power. As she grapples with the decision of whether to keep her breasts, her ovaries, both, or neither (she reveals her choice midway through the book), she continues to nurse her young daughter and to live with the fear that descend­ed when her mother died. “I would think about this in the sleepless early mornings, when my daughter pressed her hot heels into the small of my back, and I knew I was the only thing that protected her from the cold wind of fear and freedom that came into the room through the open balcony door. Then she would tap me on the shoulder and ask me to turn around so she could hold my breasts.”

A book about a medical arena of ­whip-­quick advancement is necessarily of the moment. The numerous ­up-­to-­the-­minute scientific break­throughs mentioned in the text indicate that 

 may not have a long shelf life, but Gessen is to be commended for creating a valu­able snapshot of a domain that gains a greater hold on our lives by the year. “If there is one thing behavioral geneticists can agree on,” she writes, “it is that all of their findings are nothing but a rea­son to do fur­ther studies.” Perhaps 

 may be taken in the same spirit: as a foundational early comer to the literary canon of a burgeoning ­field.

. She lives in Minneapolis, where she teaches at the Loft Literary Center. 

"Blood Matters: From Inherited Illness to Designer Babies, How the World and I Found Ourselves in the Future of the Gene" 

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Bonnie J. Rough on the rapidly changing world of the gene. 