Zoobiquity by Barbara Natterson-Horowitz Read Free Book Online Page B

noticeable feature of Tessa’s vest were the two words stitched in black thread across her midriff: “Cancer Survivor.”
    Tessa is a black Labrador retriever I met in the spring of 2010 at a gathering of pet patients who had battled illnesses and won. Although a brown lesion on the gum behind her lower left fang was still visible, her mouth cancer had been in remission for two years.As I patted Tessa’s furry, wedge-shaped head, her owner, Linda Hettich, explained how she had discovered her dog had the disease. They were playing fetch and Tessa brought back a bloody tennis ball. A trip to the vet confirmed a cancer diagnosis, and Tessa went into treatment. Although Hettich’s distinct alto voice (she’s the noon anchor for a Los Angeles news radio station) conveyed gratitude that Tessa’s cancer had not returned, her face betrayed a certain grim anxiety. Tessa was not her first dog to have cancer. A few years earlier, her beloved mutt, Kadin, had died of it. Hettich admitted in a whisper that she sometimes wonders why two of her dogs have fought the disease.
    “With Kadin, there was a tremendous amount of guilt,” she told me. Now that Tessa has had cancer, she said, there are moments when she wonders, “I’m two for two—what did I do?”
    That didn’t surprise me a bit. I’d heard “What did I do?” before; that question frequently plagues many human cancer patients, too.
    One of my roles at UCLA involves caring for people who’ve developed heart problems as a side effect of their cancer treatments. Sometimes they share with me their personal theories for why they drew the cancercard. Often, it’s something they did:
My cell phone. My deodorant. My char-grilled salmon. My microwave. My lipstick. My plastic Evian bottle. My years as a flight attendant
. Or something they didn’t do:
Missing church. Not exercising. Skipping mammograms
. Something that was done to them:
My father’s nicotine addiction. The fluoride in my water. The new carpet at my office
. Or general stress:
A lingering lawsuit. A mountainous credit card balance. Caring for an aging parent
.
    I understand that these narratives allow patients to feel a modicum of control in the face of a terrifying diagnosis. Because that in itself can be healing, I usually just listen quietly as I measure their blood pressure, check their pulses, and place my stethoscope over their heart. But some seem to be seeking medical absolution, so I gently remind them of something they’ve surely heard before: cancer has many causes. Within the DNA we inherited from our parents, from our great-great-great-grandparents, and from ancient animal ancestors lie the blueprints and machinery that instruct cells to create and maintain our body parts. But when this machinery contains errors and then malfunctions, the out-of-control growth we call cancer can develop.
    Here’s what I mean. Living, growing organisms must constantly replace old and dying cells with fresh, new ones. Making a new cell requires copying every single one of the almost three billion building blocks (called nucleotides) in the cell’s DNA. This provides the daughter cell with the exact same information as its parent. When all goes well (and, astonishingly, it usually does), the DNA is copied exactly. But occasionally, about once every ten thousand nucleotides, a mistake is made. Chemical codes can be left out, duplicated, or put in the wrong place.
    Much of the time, these slipups—called mutations—are caught by the cell’s chemical “proofreaders” and fixed before they wind up in a new cell. Often, a “typo” sneaks through but it’s not significant and the cell can continue along normally, even with the misprint. Sometimes these mistakes occur in critical regions of the DNA and actually enhance cell function. These minor changes, over time, can produce new traits, new behaviors, and even new species. For example, alterations or mutations are responsible for size differences in dog