万物简史 第582期:生命的物质(8)（在线收听）

As laboratory specimens fruit flies had certain very attractive advantages: they cost almost nothing to house and feed, could be bred by the millions in milk bottles, went from egg to productive parenthood in ten days or less, and had just four chromosomes, which kept things conveniently simple.

作为实验样品，这种果蝇有着某些无可比拟的优点：它们所占的空间极小；几乎不需要消耗食物；在牛奶瓶中就可以轻而易举地培育出数百万只；从虫卵到成虫只需要10天左右的时间；只有4对染色体，用它们做实验非常方便。

Working out of a small lab (which became known inevitably as the Fly Room) in Schermerhorn Hall at Columbia University in New York, Morgan and his team embarked on a program of meticulous breeding and crossbreeding involving millions of flies (one biographer says billions, though that is probably an exaggeration), each of which had to be captured with tweezers and examined under a jeweler's glass for any tiny variations in inheritance. For six years they tried to produce mutations by any means they could think of — zapping the flies with radiation and X-rays, rearing them in bright light and darkness, baking them gently in ovens, spinning them crazily in centrifuges — but nothing worked. Morgan was on the brink of giving up when there occurred a sudden and repeatable mutation — a fly that had white eyes rather than the usual red ones. With this breakthrough, Morgan and his assistants were able to generate useful deformities, allowing them to track a trait through successive generations. By such means they could work out the correlations between particular characteristics and individual chromosomes, eventually proving to more or less everyone's satisfaction that chromosomes were at the heart of inheritance.

在纽约哥伦比亚大学谢摩尔宏楼的一个小实验室里（后来势必得了个“果蝇室”的名字），摩尔根和他的同伴小心翼翼地培育和杂交了数百万只果蝇（有一个生物学家说有数十亿只，这也许有点夸张）。它们中的每一个都得用镊子夹住，然后在珠宝商的放大镜下观察它们在遗传方面任何微小的变化。为了生成突变体，在长达6年的时间里，他们想尽了种种办法：将这些果蝇用X射线辐射，在明亮的光线或黑暗中加以培育，在烤箱里轻轻烘烤，用离心机猛烈地摇晃——但是所有这些办法都不奏效。摩尔根几乎准备放弃他们所有的努力了。突然，一种奇特的变体重复不断地出现了——有一只果蝇的眼睛是白色的，而一般情况下果蝇的眼睛是红色的。有了这一突破，摩尔根和他的助手再接再厉，培育出了有用的突变个体，从而能在其后代中跟踪一个特性。这样，他们就研究出了特定的特点和某种特定的染色体之间的相互关系，从而在某种程度上令人满意地证明了染色体在遗传过程中的关键作用。