In animal cell culture (especially mammalian systems), what does the term “transformation” specifically mean? Provide the best interpretation used in cell biology laboratories rather than in bacterial genetics.

Introduction / Context:
In mammalian cell culture, the vocabulary differs from microbial genetics. The word “transformation” is often confused with DNA uptake. In bacteria, transformation means acquisition of exogenous DNA. In mammalian cell biology, however, transformation generally refers to phenotypic changes that confer indefinite proliferation and tumor-like characteristics (loss of contact inhibition, altered morphology, anchorage-independent growth).

Given Data / Assumptions:

• The setting is animal (mammalian) cell culture terminology.
• We must choose the cell biology meaning, not the bacterial genetics meaning.
• Typical transformed traits include faster doubling, altered karyotype, and reduced growth controls.

Concept / Approach:
Disambiguate terms: in mammalian culture, DNA delivery is properly called transfection (chemical, lipid, or electroporation methods). “Transformation” refers to the acquisition of neoplastic characteristics, either spontaneously or by oncogene/virus exposure. Therefore, the correct choice is the phenotypic change definition.

Step-by-Step Solution:

Verification / Alternative check:
Standard texts describe “transformed” lines as continuous/immortalized, often aneuploid, with reduced contact inhibition and altered morphology.

Why Other Options Are Wrong:

• A: DNA uptake in mammalian cells is called transfection, not transformation.
• C: Mixing definitions causes confusion; only (b) fits mammalian usage.
• D/E: Not relevant to accepted terminology.

Common Pitfalls:
Applying bacterial terms to mammalian contexts; assuming any genetic change equals transformation.

Final Answer:
Phenotypic modification of cultured cells toward a neoplastic or indefinite-growth state