Primary cells will grow for only a ______ time in culture but _____ many of the characteristics of cells in vivo.

• A. Unlimited; lose
• B. Limited; retain
• C. Short; transform
• D. Permanent; retain

Answer: (B)

Primary cells have a finite lifespan in culture, yet they closely preserve many of the features of the cells from which they came. Because they’re taken directly from tissue, their gene expression, morphology, and functional characteristics reflect the in vivo state, especially at early passages. Their proliferative capacity is limited by cellular senescence and telomere shortening, so they can’t keep dividing indefinitely the way some immortalized cell lines can. Over time in culture, they may gradually change, but initially they retain much of the tissue-specific behavior observed in the body. This is why primary cells grow for a limited time but still retain many in vivo characteristics.