In the Search to Discover the Agents That Cause Mad $\bullet$

In the search to discover the agents that cause mad cow disease,scrapie in sheep,and CJD and kuru in humans,diseased brain tissues were passed through a fine filter to remove bacteria.The filtrate was still infectious,indicating that something smaller than bacteria,either viruses or organic molecules,must be the causative agent.If a virus was responsible for these brain diseases,then the infectious agent would contain either RNA or DNA.Other possibilities were that the agent was a carbohydrate,fat,or protein.Tissue filtrates were treated with agents that destroyed just one of these chemicals and then injected into a healthy animal,with the results as follows.What is the infectious agent? $\bullet$ Amylase digests carbohydrates; tissue filtrate still infects healthy test animal.
$\bullet$ Lipase digests fats; tissue filtrate still infects healthy test animal.
$\bullet$ Formaldehyde and/or heat denatures DNA and RNA; tissue filtrate still infects healthy test animal.
$\bullet$ Trypsin digests protein; tissue filtrate does not infect healthy test animal.

A) carbohydrate
B) fat
C) protein
D) DNA or RNA
E) Could be carbohydrate,fat,or DNA or RNA but not protein.