Animal eggs were cloned by scientists to create human embryonic stem cells. This cells were developed all right but as soon as their nuclei were replaced with human nuclei everything went wrong.The DNA could not be reprogrammed as the same genes were not activated.
The scientists at Advanced Cell Technology had thought of substituting human eggs for animal eggs as the former were not easily available. One of the primary reason for the shortage being ethical concerns.
So the only other alternative is to continue research works with skin cells.They can be identically reprogrammed into embryonic stem cells but they are clinically very harmful since dangerous viruses are used for their cultivation.
Another important issue which needs focus is that experiments with human embryo shows high failure rates. Almost hundreds of human eggs are required to create a single stem line, which is not at all practical and economical.
However the scientists are not ready to give up so early. They would continue their researches on both fronts as their is no word called “impossible” in the dictionary of a scientist. So let’s crossed our fingers and see what happens in the long run…..