In a process that is an improvement over the methods used with Dolly, Ryuzo Yanagimachi, of the University of Hawaii, has demonstrated a nuclear transfer technique that has come to be known as the Honolulu Method. This technique uses a micropipette (small glass tube) to insert the nuclear material. Working with mice, cloning is accomplished using nuclei from "cumulus cells," which surround a developing ovarian follicle. Using a micropipette, they inject donor nuclei from the cumulus cells into enucleated egg cells. Then, the eggs are prevented from dividing into blastocysts for five to six hours. This delay has proven crucial. Due to unknown cellular mechanisms, many more oocytes develop into blastocysts when the delay is introduced.
In a more recent development, seven piglets carrying human genes for Alzheimer ’s disease were born in Norway in 2007. Scientists Arne Lund Jørgensen at Aarhus University and Gábor Vajta at University of Copenhagen developed the specially modified piglets using a technique called “handmade cloning.”
In this procedure, the donor egg cells outer shell, or zona pullicida is first dissolved with an enzyme. Then the genetic material – the chromosones and centrosome is identified, now on the surface of the cell, by direct observation using a microscope. A microblade is used to sever the chromosome and remove it, creating an egg without genetic material. Then, using a skin cell that carries the Alzheimer’s gene, an electrical shock is used to fuse the two cells together. After waiting one hour, the fused cells are merged with a second chromosome-free cell, and the egg then contains the complete genetic material from both the fibroblast and the skin cell. Electrical and chemical stimulation is provided to hasten cell division. Then the cells are cultivated in a special solution for zona pullicida free cells until they develop into a blastocyst.
Next: The Future Benefits of Cloning
Remembering Dolly: The History, Promise, and Future of Cloning
It was a different time and a different world. Dolly the sheep's soulful eyes reached out to us and ignited a world-wide controversy about cloning. More than a decade has passed, but has much changed? Here we'll look at the past, future, and possible promise of animal and human cloning.