2. Isolated Tissue Cell or tissue culture in vitro Primary culture Secondary culture Sub-culture Cell Line Sub-culture Immortalization Successive sub-cultureSingle cell isolation Cloned cell line Senescence Transformed cell line Loss of control of cell growth Cell Strain

3. Revive frozen cell population Isolated from tissue Maintain in culture (aseptic cinditions) Sub-culture (passaging) Cryopreservation Typical cell culture flask ‘Mr Frosty’ Used to freeze cells

4. DOUBLING TIME : Time taken by cells to double the population. CELL LINE : When the primary culture is first sub-cultured or passaged. CELL STRAIN : When a particular type of cell lineage is selected, characterized and cloned it is called a cell strain. PASSAGE NUMBER : The number of times a culture has been sub-cultured.

5. Primary cultures Derived directly from animal tissue, embryo or adult. Cultured either as tissue explants or single cells. Initially heterogeneous – containing various types of cells. Finite life span in vitro. Retain differentiated phenotype. Mainly anchorage dependant. Exhibit contact inhibition. Types of cell cultured

6. Secondary cultures Derived from a primary cell culture. Isolated by selection or cloning. Becoming a more homogeneous cell population that is contains a specific cell type. Finite life span in vitro. Retain differentiated phenotype. Mainly anchorage dependant. Exhibit contact inhibition.

7. Types of cell cultured Continuous cultures Derived from a primary or secondary culture Immortalised: Spontaneously By transformation Serially propagated in culture showing an increased growth rate Homogeneous cell population Loss of anchorage dependency and contact inhibition Infinite life span in vitro Differentiated phenotype: Retained to some degree in cancer derived cell lines Very little retained with transformed cell lines Genetically unstable

8. NEED TO PASSAGE CELLS:-  To maintain cells in culture.  To increase cell number for experiments/storage Check confluency of cells Remove spent medium Wash with PBS Resuspend in serum containing media Incubate with trypsin/EDTA Transfer to culture flask 70-80% confluence 100% confluence Checking confluency of cells