Is the world ready for another Dolly? With the recent development of the technology to successfully produce a human cloned embryo in Seoul, South Korea, two weeks ago, it is evident that cloning has taken a giant leap forward.

More and more researchers are pushing for the advancement of therapeutic cloning and stem cell research to clone parts of humans.

Dr. Sarah K. Bronson, assistant professor of cellular and molecular physiology at the Penn State College of Medicine, works with embryonic stem cells as a medium to examine genetic changes in mice and to study stem cell lineage.

"I am particularly interested in the development of the cell that forms and mineralizes the bone matrix, the osteoblast," Bronson said. "While there is a great diversity of cellular and molecular research in this department, my group is the only one that works principally on stem cells and stem-cell differentiation."

Bronson believes that therapeutic cloning shows great promise for improving the effectiveness of treating human developmental disorders, injuries and diseases.

"Reproductive cloning of humans is an activity that is extremely short-sighted and irresponsible, and it is hard for me to envision my opinion of that changing in my lifetime," Bronson said. "In terms of the ethics of using embryos generated by in-vitro fertilization of donated eggs and sperm, if the donors give their consent, I think that should be adequate. I don't feel that there is anything sacred about a blastocyst-stage embryo," she said.

However, Bronson is skeptical that the human will be successfully cloned in the near future.

"Frankly, I have worked with mouse embryonic stem cells since the early 1990s, and I was surprised at the relative ease with which people were able to generate human embryonic stem cell lines. That tells me that the pace of research is pretty unpredictable," she said. "I would like to think it would take a long, long time for someone to achieve reproductive cloning in humans, but I am afraid that the combination of the technology 'not being rocket science' and the ready availability of people crazy enough to participate in just about anything means that it might not be long at all."

Cloning parts and whole organisms has, however, been an integral part of science and agriculture for a long time. Mark Guiltinan, professor of plant molecular biology in the department of horticulture, works with plant tissue cultures and somatic embryogenesis. According to Guiltinan, the process of manually replicating plants is a natural process that scientists have been taking advantage of for a long time.

"In plant systems, cloning is a naturally occurring process. Some plants propagate asexually, such as plants that have runners on the ground, like strawberries; and when this happens a new strawberry forms," Guiltinan said.

Scientists are merely taking advantage of what nature already provides, he said.

"From years of research, we've been able to learn that plant cells are able to regenerate whole organisms," Guiltinan said.

He added that while most plants are totipotent, meaning they have the ability to regenerate parts, most animals are not. This is the biggest difference when cloning animal and plant parts is concerned.

Nevertheless, plant tissue cloning has a lot of important applications for the future for conserving plants and making them more useful.

"As the population grows, there is a bigger demand for foods, which calls on a greater need for plants and endangers some species of plants," Guiltinan said.