Wiping away doubts that Dolly the sheep clone was a fluke,
University of Hawaii researchers announced they’ve been cloning mice for months,
creating a flock of more than 50 duplicate rodents along the way. 71. The
success of the Hawaii group transforms adult cloning from a scientific novelty
to a well-defined procedure likely to be .reproduced in labs around the world.
The mass production of carbon copy mice, in turn, now allows researchers to test
variations of the cloning techniques to see what works best. Cloning the
genetically engineered mice used in medical studies should also be cheaper than
current breeding methods. The Hawaii researchers use essentially
the same recipe used to make Dolly: Take an egg. Scoop out the nucleus, which
contains the DNA genetic information, and discard. Take a cell of the animal you
wish to clone and insert its DNA into the egg. Add chemicals to tell the egg to
start developing into an embryo. Incubate the embryo in a test tube for a few
days, and then implant it into a foster mother. Wait for the foster mother to
give birth to the clone. 72. Where they modified the recipe was the method
for moving the DNA from the animal-to-be-cloned into the egg. Most researchers
had thought that mice would be particularly difficult to clone, because the DNA
in mice embryos switches on very early, possibly as soon as the egg splits into
the two-cell stage. Because adult cells have specific,
specialized functions, most of the unused DNA has been turned off. Scientists
had thought that the implanted DNA would not have enough time to "repro- gram"
itself back to the embryonic, unspecialized state. Thus, most cloning research
has focused on animals where the DNA switches on later, allowing more time for
the reprogramming. 73. In cows, for example, the DNA switch-on occurs when
the embryo reaches the eight-cell stage. No one is sure how the ttawaii group
got the mouse DNA to reprogram itself more quickly, but some have the suspicion
that getting rid of the outer part of the adult cell speeds the
process. In addition to various genetic tests, the
researchers used a simple color scheme to verify that the DNA of the babies was
not contaminated by either the egg donor or the foster mother. The eggs came
from black mice, while the foster mothers were all white mice. The baby mice all
came out coffee-colored, the color of their identical DNA mother. The
researchers have licensed their technology to venture capital company ProBio
America Inc. , based in Honolulu. "This technique we are expanding into the
large commercial animals, such as cows and sheep, where much of our business is
intended to be," says ProBio’s Cameron Reynolds.