What milestone did Dolly the sheep cloning case demonstrate?

• A. It showed cloning of a mammal is possible
• B. It proved cloning is unethical
• C. It proved all cloned animals are sterile
• D. It solved energy issues

Answer: (A)

The key idea here is that cloning a mammal from an adult cell is possible. Dolly demonstrated this by using somatic cell nuclear transfer: a nucleus from an adult sheep’s mammary cell was placed into an enucleated egg, the embryo was grown and implanted into a surrogate, and Dolly was born. This showed that specialized adult cells can be reprogrammed to an embryonic state and develop into a whole organism, a landmark achievement in biotechnology.

The other statements aren’t the milestone Dolly established. Cloning being unethical is a debate and not the demonstrated capability; Dolly’s case doesn’t prove any moral conclusion. The claim that all cloned animals are sterile is incorrect—Dolly herself produced offspring, showing that sterility isn’t a universal rule for clones. And energy issues are unrelated to cloning breakthroughs.