From the BBC:
Scientists say they have demonstrated that animals can defy the laws of genetic inheritance. Researchers found that mice can pass on traits to their offspring even if the gene behind those traits is absent. The scientists suggest RNA, a chemical cousin of DNA, passes on the characteristic - in this experiment, a spotty tail - to later generations.
The research focuses on a gene called Kit, which comes in two varieties: "normal" and "mutant".
This explains everything!