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 were 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.

Question

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 were 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.

Quizplus · Accepted Answer

CJD, kuru, mad cow disease, and scrapie are caused by prions--infectious proteins. This was supported by the finding that only trypsin, which digests proteins, was able to deactivate the infectious agent.

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

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