Q.58 Given below are two statements :

In the light of the above statements, choose the correct answer from the options given below :

1. Both Statement I and Statement II are true
2. Both Statement I and Statement II are false
3. Statement I is true but Statement II is false
4. Statement I is false but Statement II is true

   Statement I is true but Statement II is false. Prions exhibit remarkable resistance to heat up to 90°C due to their protein-only composition, while they are notably resistant to radiation, making Statement II incorrect.

   Prion Properties

   Prions are infectious misfolded proteins lacking nucleic acids, explaining their unusual stability. They resist denaturation at temperatures up to 90°C or beyond, surviving standard autoclaving at 121°C for short durations but requiring harsher conditions like 134°C for 18 minutes for inactivation.

   Statement Analysis

   • Statement I (True): Prions withstand 90°C without inactivation, as their beta-sheet structure remains intact under such heat.​

   • Statement II (False): Prion infectivity shows high resistance to radiation (UV, gamma), which targets nucleic acids but spares pure proteins; doses up to 100 kGy only partially reduce infectivity.

   Option Breakdown

   Option	Explanation	Correct?
   Both true	Incorrect; ignores prions’ radiation resistance.	No ​
   Both false	Incorrect; overlooks verified heat resistance.	No ​
   I true, II false	Matches evidence: heat-resistant but radiation-resistant.	Yes
   I false, II true	Incorrect; contradicts both properties.	No ​

   Prions not inactivated by 90°C heat yet resistant to radiation treatment sensitivity define their unique infectious nature, crucial for GATE Life Sciences aspirants tackling prion statements.

   Prion Structure Basics

   Prions are rogue proteins (PrP^Sc) converting normal PrP^C, devoid of DNA/RNA. This explains prions not inactivated by 90°C, as heat alone fails to disrupt their stable conformation.

   Heat Resistance (Statement I True)

   Standard sterilization up to 90°C leaves prions infectious. Autoclaving needs 134°C/18 min or NaOH/SDS combos for effective denaturation.​

   Radiation Effects (Statement II False)

   Radiation targets nucleic acids, irrelevant for prions. Gamma doses (50-100 kGy) yield only partial log reductions, not full inactivation.

   GATE Exam Relevance

   This question tests resistance profiles: prions not inactivated by 90°C radiation treatment sensitivity is false, affirming option (3).​