Differentiate between finite and continuous cell lines.
Finite cell lines have a limited number of cell divisions and a limited life span. These are derived from primary cultures of normal cells. As cells pass several times during sub-culturing, they lose their ability to proliferate, a process called senescence.
Continuous cell lines arise when some cells of a finite cell line undergo transformation and resume the ability to divide indefinitely. This transformation can occur spontaneously or be chemically or virally induced. These cell lines are immortal and tumorigenic, less adherent, can grow in suspension, are fast growing, less demanding for nutrients, and can grow to higher cell density. They can be sub-cultured indefinitely as permanent cell lines.
Explanation
The textbook clearly distinguishes finite and continuous cell lines based on lifespan, division capacity, origin, and characteristics. Finite cell lines are derived from primary cultures of normal cells and undergo senescence after limited divisions. Continuous cell lines arise from transformation of finite cell lines (spontaneously or induced) and are immortal, tumorigenic, fast-growing, and less demanding for nutrients. The key differences include lifespan (limited vs indefinite), growth characteristics, and nutrient requirements.