How Dolly was born

Professor Wilmut's experiment involved three adult female sheep. He first     1     (take) a cell from sheep A, He then implanted (植入) the genetic information into     2     (it) nucleus (细胞核) with an egg cell from sheep B, whose nucleus had been removed. Tiny electric shocks     3     (use) to stimulate ( 激 发 ) this new “combination” egg cell to divide.     4     (final), the new embryo was implanted into the body of sheep C, where it developed just like any other sheep embryo.

In 1996, his determination and     5     (patient) paid off. Dolly became the first sheep to be born without a father and was also the first genetically     6     (identity) copy of an adult. As the egg cell gradually splits, its millions     7     offspring cells specialize into muscle cells or skin cells, for example,     8     (mouse) and cattle have now also been cloned from an adult. These clones have also been cloned, producing three generations of healthy clones.

    9     was thought that a specialized cell could never become a different cell, with all the genetic instructions     10     (form) the entire creature.