Biotechnology Question Bank, Chimeric Mouse, Plant Cell Culture

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8. Fill in the blanks:

(a) ------------ was the first drug to be produced by mammalian cell culture.(b) ------------- are used for scaling up the production of suspension cells.(c) In----------- the cells adhere to the total curved surface of the microcarrier beads.(d) An------------- microscope is used for visualizing cell cultures in situ.(e) ------------------involves the storing of cells at very low temperature.(f) ---------------------is a highly effective therapeutic agent who reverses acute renal allograft rejection.(g) ------------------play a major role in rejecting foreign tissue in transplantation.(h) The animal cells in culture exhibit the phenomenon of --------------- (i) The maintenance of growth of the cells in culture medium is known as ------------------- (j) ------------------ are those cell lines which have a limited life span and they grow through a limited number of cell generations.(k) Cell lines transformed under in vitro culture conditions give rise to-------------------

Ans (a) Tissue plasminogen activator, (b)Spinner cultures, (c) Roller bottles, (d) Inverted microscope, (e) Cryopreservation, (f) OKT3, (g) T cells, (h) Contact inhibition, (i) primary cell culture, (j) Finite cell lines, (k) Continuous cell line

9. What is a chimeric mouse?

  • Embryonic stem cells are cell lines directly derived from the inner cell mass of fertilized mouse embryo without the use of immortalizing or transforming agents. It fertilized mouse egg is grown in culture (in vitro fertilization), it is observed that after several steps of cleavage, the cells which are dividing get accumulated in one corner.

  • These cells are called inner cell mass (ICM cells) cells. These cells could be maintained in tissue culture in the presence of irradiated fibroblast cells. It was observed that these cells could be used to create chimeric mice. In chimeric mice, it was possible to take ES cells from a black mouse and implant it into the embryo of an albino (white) mouse. The progeny so developed had skin colour of black and white (a chimera).

10. What are the differences between plant cell culture and animal cell culture?

  • The plant cells in culture can grow indefinitely if the nutritive media is constantly replenished. However, the animal cells, depending on the tissues they have been isolated from can grow even in the best nutritive media to limited generations.

  • The animal cells also exhibit contact inhibition i.e. when cells grow and reach the walls of the container they are prevented from further growth. Another important feature of cell growth in culture is that their environment is different from that in vivo.

  • The other major differences include the absence of cell-cell interaction, cell-matrix interaction etc.

11. What is Embryonic stem cell culture?

  • Embryonic stem cells are cell lines derived directly from the inner cell mass of fertilized mouse embryo without use of immortalizing or transforming agents. If we fertilized a mouse egg and grow it in tissue culture, it is observed that after several steps of cleavage, the cells which are dividing get accumulated in one corner. These cells are called inner cell mass (ICM) cells.

  • These cells could be maintained in tissue culture in the presence of irradiated fibroblast cells. These cells could retain the characteristics of the embryo founder cells, even after prolonged culture and extensive manipulation. The cells reintegrate fully into embryogenesis when returned to the early embryo. The cells would be used to create chimeric mice and to maintain a stable euploid karyotype. The cells would renew without differentiating in culture.

12. How many categories of cell lines are available?

The various types of cell lines are categorized into two type’s i.e. finite cell lines and continuous cell lines.

(a) Finite cell lines- Finite cell lines are those cell lines which have a limited life span and they grow through a limited number of cell generations. Finite cell lines show the property of contact inhibition, density limitation and anchorage dependence. The mode of growth is in the monolayer form. The growth rate is slow and doubling time is around 24 to 96 hrs.(b) Continuous Cell lines- Cell lines transformed under in vitro culture conditions give rise to continuous cell lines. The various properties associated with continuous cell lines are, the ploidy- either aneuploid or heteroploidy. There is no contact inhibition and no anchorage dependence. The mode of growth is either monolayer or suspension form. The growth rate is rapid and doubling time is 12 to 24 hours.

13. What do you understand by the term hybridoma technology?

  • Antibodies obtained from serum are a heterogeneous population of proteins released by different populations of B lymphocytes and therefore are known as polyclonal antibodies and bind very specifically to an epitope or an antigen. They are produced from antigen activated B lymphocytes cells that have been immortalized by hybridizing (fusing) them with a myeloma cell (cancerous lymphocyte).

  • Ceaser, Milstein and George Kohler developed the immortalized hybridoma cell line by fusion of antibody producing B cells and cancerous cell (myleoma) in presence of polyethylene glycol (PEG). Thus, the hybrid retains the ability of the B cells to secrete antibody and the ability of the myeloma cell to grow indefinitely. The Hybridoma technology has created a revolution in the area of diagnostics and antibody based therapy.

14. What is the importance of karyotyping in established cell lines?

  • Once a cell has been established, its karyotype is determined. This will confirm the species of origin, at least for those cells karyotyped, and determine the extent of gross chromosomal changes in the line. Karyotypes may vary from being near normal to being aneuploid. While a normal karyotype is desirable, the presence of an abnormal karyotype is desirable, the presence of an abnormal karyotype does not preclude using the cells for in vitro studies, especially if it has been demonstrated that the cells retain the normal function expected of them.

  • If a normal karyotype is required e.g. to create transgenic animals, then special care is taken in handling the cells to minimize chromosomal changes. The stability of the karyotype depends on the species from which they are derived, the growth conditions used, the way in which the cells are sub cultured, and whether or not the cells are frozen.

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