Animal Tissue Culture and Animal Biotechnology
This section covers animal cell culture and animal biotechnology. The exam tests aseptic technique, media, cell lines, subculturing, cryopreservation, and products such as vaccines and monoclonal antibodies.
Core rules
Animal cells are grown in complex medium containing amino acids, vitamins, salts, glucose, and usually animal serum such as fetal bovine serum. Antibiotics are added, and incubators maintain about 37 degrees Celsius with 5% carbon dioxide and high humidity. Primary cultures come directly from tissue and have a finite lifespan. Continuous or immortalized cell lines can be subcultured repeatedly; HeLa is a well-known example. Adherent cells need a surface and are detached with trypsin-EDTA; suspension cells grow in stirred or shaking culture. Subculturing maintains log-phase growth. Cryopreservation uses a cryoprotectant such as DMSO or glycerol and liquid nitrogen. Applications include viral vaccine production, monoclonal antibodies from hybridomas, recombinant proteins, toxicity testing, and research on gene therapy.
Worked example
A T-75 flask contains 3 x 10^6 cells. A 1:3 split gives approximately 1 x 10^6 cells per new flask. The passage number increases by one. If the cells are contact-inhibited, they stop dividing at confluence, so subculturing before full confluence keeps them healthy. The reasoning is that the same cell number is divided among three vessels, not that the cells triple.
Traps that cost marks
Serum is not a defined medium component and can vary between batches. Primary cells are not immortal. HeLa cross-contamination is a classic problem. Trypsin is used for detachment, not for sterilization. Cryopreservation requires slow cooling and a cryoprotectant; direct freezing kills cells.