Question

Match List-I with List-II

List-I & List-II
(A). Discontinuous heating & (I). UV rays
(B). Destruction of all viable forms including spores & (II). Gamma rays
(C). Ionization of biological molecules & (III). Tyndallization
(D). Pyrimidine dimerization & (IV). Steam sterilization under pressure
Choose the correct answer from the options given below:

• (A) - (I), (B) - (II), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (I), (C) - (IV), (D) - (II)
• (A) - (I), (B) - (III), (C) - (IV), (D) - (II)
• (A) - (III), (B) - (IV), (C) - (II), (D) - (I)

Hint:

To remember:
- Steam under pressure (autoclave) is the standard method for sterilizing laboratory media because it kills heat-resistant endospores.
- UV radiation is used for surface disinfection, but has poor penetrating power.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Sterilization and disinfection involve physical or chemical methods used to eliminate microorganisms from surfaces, liquids, or instruments.

Step 3: Detailed Explanation:
Let us match the concepts in List-I with the methods in List-II:
- (A). Discontinuous heating: This process, also known as Tyndallization, involves boiling substances at \(100^{\circ}\text{C}\) for 20-45 minutes on three consecutive days.
The intermediate incubation periods allow heat-resistant bacterial endospores to germinate into vulnerable vegetative cells, which are killed during the next heating cycle, matching (III).
- (B). Destruction of all viable forms including spores: This is the definition of complete sterilization.
It is achieved using an autoclave, which provides steam sterilization under pressure (typically \(121^{\circ}\text{C}\) at 15 psi for 15 minutes), matching (IV).
- (C). Ionization of biological molecules: High-energy electromagnetic radiation, such as Gamma rays, ejects electrons from cellular molecules, generating highly reactive free radicals that damage DNA. This is called ionizing radiation, matching (II).
- (D). Pyrimidine dimerization: Non-ionizing radiation, such as UV rays (especially at 260 nm), is absorbed by DNA bases.
This absorption causes the formation of covalent bonds between adjacent pyrimidine bases (thymine dimers), disrupting DNA replication, matching (I).
This gives the matching: (A) - (III), (B) - (IV), (C) - (II), (D) - (I).

Step 4: Final Answer:
The correct match is Option (D).