Free Radicals - Michael Brooks [77]
You get a hint of McClintock’s steely resolve in the face of such criticism when you hear the story behind her name. Her parents initially called her Eleanor, but decided that was too delicate and feminine. ‘Barbara’ McClintock encapsulated her temperament much better, apparently. Perhaps it was because St Barbara was the protector against lightning strikes and firestorms, or simply because the name means ‘outsider’ or ‘foreigner’. How her parents had such foresight, it is hard to know.
In December 1941, McClintock began working at the Carnegie Institution of Washington’s research facility on Long Island, New York. The laboratory, a genetics research station where plant breeders tried to find the roots of heredity, was called Cold Spring Harbor. McClintock, now thirty-nine years old, had been offered a one-year research post, but she was destined to enter her fifth and sixth decades still working for the Institution. Until this point she had flitted around, working in Germany, in California, in Missouri and at Cornell. On Long Island, though, she found what she had been searching for: the chance to immerse herself fully in discovery.
McClintock’s speciality was the genetics – the hereditary characteristics – of maize. Just as you and I have a certain hair and eye colour, or fingernail shape, that we get from our parents, maize plants have characteristics, notably the colour of leaves and kernels, that are determined by their parent plants. McClintock grew hundreds of maize plants at a time and kept track of their parentage. In fact, she did more than that: she sidelined the role of wind and insects, and pollinated them by hand.
Each kernel of corn comes from a single egg, one of thousands on the plant. The fertilising pollen comes either from the same plant, or from a neighbouring plant and carried across by the wind or by insects. Each egg can thus be fertilised from an entirely separate plant. This is a recipe for a huge amount of variation within a single organism. For a geneticist, that is both a blessing and a curse: the variation gives the potential for interesting traits to be selected for. But with so many variables, it is easy to lose track of the data so vital to a scientific understanding.
McClintock, though, was thorough, passionate and single-minded. Though she regarded many colleagues as friends, she was uninterested in personal attachments beyond friendship. She once told her biographer, Evelyn Fox Keller, that ‘I just didn’t feel it. And I could never understand marriage.’ She was, in many ways, entirely suited to this lonely task, heading out into her Long Island maize fields in the early morning to focus all her attention on kernels of corn, the waxy striped leaves, and the molecular structures within the plant that gave rise to all its characteristics.
In 1944, McClintock noticed something odd in a plant she had labelled B-87. Its yellow kernels were speckled with red and purple spots. There was nothing intrinsically peculiar in this; it was the way the spots had appeared that caught McClintock’s attention. Each kernel starts out as a single cell that repeatedly divides. With each division, a copy of the genetic recipe for the cell is passed on. Because every cell has the same recipe, its colour – the default is yellow – should be consistent. If it isn’t, a gene for colouring the cell with a pigment – turning it purple or red, for instance – must be turning on sporadically. What McClintock’s keen eye noticed in B-87 was that, though the pigmentation was sporadic, it was far from random.
The standard theory of inheritance