Earlier this week, researchers published in the journal Cell that they had created embryonic stem cells by cloning human skin cells.
An embryo is usually created when sperm enters the egg cell, which then starts to divide. Instead of using sperm, scientists extracted DNA from the skin cells of an eight-month old baby with a genetic disease. The DNA was transferred into a hollow human egg cell, and scientists used chemicals to help the cell divide as a regular fertilized egg would.
After several days, the cells multiplied enough to form an embryo that was genetically identical to the 8-month-old baby. Scientists then extracted stem cells from this embryo, which was destroyed in the process.
As embryos are a collection of cells that could potentially develop into fully formed humans, the destruction of embryos during the extraction of stem cells is what makes the process so controversial. However, scientists in this particular study say the embryos being used would not have developed further, as that required another chemical process that was not introduced in the research.
This animation explains the cloning process.