What are primary cells that have been transformed to grow more or less indefinitely called?

• A. Immortalized cells
• B. Primary cells
• C. In Vitro Tests
• D. Continuous cells or cell line

Answer: (D)

When cells derived from tissue gain the ability to keep dividing beyond their normal limit, they are described as a continuous cell line. Primary cells, by contrast, come from tissue and have a finite lifespan in culture because of natural growth controls. If those cells are transformed—through genetic changes or viral factors—their growth controls are bypassed and they can be maintained and expanded indefinitely. This transformed, indefinitely propagating population is what we call a cell line. Immortalized cells is another accurate term, but the standard way to refer to the ongoing culture used for long-term experiments is continuous cells or a cell line.