21.   Then, in a process that is still not understood, they force the normal proteins to change their shapes and become like the abnormal ones.

22.   These refolded proteins were then exposed to enzymes that break down normal proteins, but not prions.

23.   Unlike disease-causing viruses or bacteria, prions are normal proteins found throughout the body tissues of humans and other animals.

24.   When the cell makes its normal proteins, it inadvertently makes the protein whose recipe is in the inserted gene.

25.   If scientists can stop the conversion of normal proteins, the brain should be able to eliminate the rest, he said.

26.   Mad cow disease is caused by an abnormal protein, called a prion, which can cause changes in normal proteins and result in deep lesions in the brain.

27.   One mouse strain had the normal Fas protein while the other mouse type lacked the protein.

28.   They know the gene makes brain cells produce a defective version of a normal protein.