1.   Because transplanted quail cells will behave normally in chick embryos, she realized she had an invaluable natural Marker.

2.   She noticed that the nuclei of the cells of the quail embryo looked slightly different from those of the chick embryo.

3.   The chick embryo proper comes from a very small region resting on the yolk and which is equivalent to the mammalian egg.

4.   When researchers tried to mimic the results on other animals, such as chick embryos, it did not have the same effect.

5.   He found that chick embryos moved in predictable ways as they developed, until they finally broke out of their shells, and that those movements were spontaneous.

6.   He took part in the clinical trial of an experimental smallpox vaccine derived from chick embryos.

7.   The last experiment was conducted in chick embryos.

8.   Then he fetches a Petri dish with a chick embryo a few days old.

9.   They inserted the mutated gene into a retrovirus, which smuggled the altered gene into the cells of chick embryos.

10.   They inserted the mutated gene into a retrovirus, which smuggled the al- tered gene into the cells of chick embryos.