Scientist Profile:
Hans Spemann
In 1928, Hans Spemann, continuing to experiment with
salamander embryos conducted the first nuclear
transfer
experiment in which he transferred the nucleus of a salamander embryo cell to a
cell without a nucleus. Using a
strand of hair as a noose as he had done in his 1902
splitting of a salamander embryo, Spemann tightened the
noose around a newly fertilized egg cell, forcing the nucleus to one side
and only cytoplasm to the other. No cell material
was allowed to pass between each isolated side of the
cell. Next, Spemann waited as the side with the nucleus
divided and grew until it was a sixteen cell embryo. Then
Spemann loosened the noose, and allowed the nucleus from
one of the embryo cells to slip over into the cytoplasm
on the other side. Finally, Spemann completely tightened
the noose, physically breaking the ball of cytoplasm and
its new nucleus off from the sixteen cell embryo. From
this single cell grew a normal salamander embryo. The
results of this experiment proved that the nucleus from
an early embryo cell was able to direct the complete
growth of a different salamander. Spemann had created one
of the first clones. Spemann published his results
in his 1938 book "Embryonic
Development and Induction" in which he called for the
"fantastical experiment" of cloning from
differentiated or adult cells.
Overview of the Nuclear
Transfer technique.
Diagram: Spemann's Nuclear
Transfer
Web Link:
Biography
of Hans Spemann
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