Andrew Atroshenko Ballerina painting

Andrew Atroshenko Ballerina painting
Albert Bierstadt On the Saco painting

Scientists have already had visible evidence that cloned animals are not normal. Nearly 98 percent of attempts to clone animals have failed and those that do survive often appear abnormal and grossly enlarged. Now researchers say they have new evidence to explain why.
By tracing specific genes in cloned mice, Rudolph Jaenisch, a biologist at Whitehead Institute at the Massachusetts Institute of Technology and colleagues, found that while clones showed no clear flaws in their genetic make-up, the animals did reveal problems in expressing their seemingly normal genes. The team traced this gene expression problem not to the cloning process itself, as scientists had suspected the problem might lie, but to the original stem cells that were used to help create the cloned mice.