**Question:** Culture media containing egg or serum is typically sterilized by using

A. Autoclaving
B. Gamma irradiation
C. Ethylene oxide
D. Filtration

**Correct Answer:** D. Filtration

**Core Concept:** Sterilization of culture media is a crucial step to prevent contamination and maintain the sterility of the media during the experimentation process. Sterilization methods include physical and chemical methods.

**Why the Correct Answer is Right:** Filtration is the correct method for sterilizing culture media containing egg or serum because it allows the passage of gases but prevents the passage of large particles and microorganisms. This ensures that the media remains sterile while allowing essential components to pass through.

**Why Each Wrong Option is Incorrect:**

A. Autoclaving (A): Although autoclaving is a common method for sterilizing culture media, it is not suitable for media containing egg or serum. Egg-based media contain proteins and lipids that are prone to degradation at the high temperatures used in autoclaving, leading to loss of viability of the cells or organisms being cultured.

B. Gamma irradiation (B): Gamma irradiation is a suitable method for sterilizing culture media, but it is not the best choice for media containing egg or serum. Irradiation can cause chemical changes in proteins and other biological components, which may affect the properties and functionality of the media.

C. Ethylene oxide (C): Ethylene oxide is a gas-phase sterilization method that is suitable for sterilizing culture media. However, it should not be considered the best choice for media containing egg or serum. Ethylene oxide can cause chemical changes and denaturation of proteins, affecting the functionality of the media, particularly for egg-based media.

**Clinical Pearl:** Filtration is a preferred method for sterilizing culture media containing egg or serum as it prevents degradation of the media components and maintains the viability of cells or organisms during the experimentation process. It is essential to consider the properties and limitations of different sterilization methods when selecting the appropriate technique for specific types of culture media.