Animal Cell Culture

Callus Cultures: Callus is an undifferentiated mass of cells that are commonly used in plant tissue culture. They can be maintained in the lab for long periods through repeated sub-culturing. They are capable of growing for indefinite periods and can be used for various tissue engineering processes. Ovary: Ovaries are parts of the plant reproductive system which contain ovules and are not typically used in long term cultures in vitro. Protoplast: Protoplasts are plant cells from which the cell wall has been removed. Protoplasts are useful in plant genetic engineering and transformation techniques, and they are used in short term experiments. Mass Cell: The term ‘Mass Cell’ is not associated with plant cell culture.

Antibiotics are added to animal cell culture medium to prevent contamination by bacteria, fungi, or other microorganisms, which can outgrow and damage the cultured cells. While animal cells do not require antibiotics for their growth, contamination can ruin the culture, making antibiotics an important precautionary measure. Two common antibiotics used in animal cell culture:

• Penicillin — inhibits bacterial cell wall synthesis.
• Streptomycin — inhibits bacterial protein synthesis.

CO₂ incubators are designed to maintain an environment optimal for animal cell cultures, which includes maintaining high humidity to prevent desiccation (drying out) of the culture medium. The pan of water inside the incubator helps sustain this humidity level, thus preventing the medium from evaporating.

• Assertion (A): True. Desiccation prevention is important for cell culture health.
• Reason (R): True. The water pan maintains the humidity needed.
• The Reason correctly explains the Assertion, so option (A) is correct.

James Thomson is credited with pioneering the technique to isolate and culture human embryonic stem cells, which opened new possibilities in regenerative medicine and developmental biology.

• James Thomson: Developed methods for isolating and culturing human embryonic stem cells.
• Ceasar Milstein and George Kohler: Known for work on monoclonal antibodies.
• George Gay: Not associated with embryonic stem cell research.

Thus, the correct answer is (B) James Thomson.