Biotechnology Question Bank, Plant Biotechnology, Gene Transfer

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16. “The Agrobacterium is considered as Natural Genetic engineer of plants.” Comment.

  • This bacterium is known as natural genetic engineer of plants since these bacteria have the natural ability to transfer T-DNA of their plasmids into plant genome upon infection of cells at the wound site and cause an unorganized growth of a cell mass known as crown gall.
  • Ti Plasmids can be used as gene vectors for delivering useful foreign genes into target plant cells and tissues. The foreign gene is cloned in the T-DNA region of Ti – plasmid in place of unwanted sequences.

17. What is direct gene transfer? What are the methods of direct gene transfer?

  • In the direct gene transfer methods, the foreign gene of interest is delivered into the host plant cell without the help of a vector. The following are some of the common methods of direct gene transfer in plants:
    • Chemical mediated Gene transfer- Certain chemicals like polyethylene glycol (PEG) and dextran sulphate induce DNA uptake into plant protoplasts.
    • Microinjection- Here the DNA is directly injected into plant protoplasts or cells using fine tipped glass needle or micropipette.
    • Electroporation-In this case, a pulse of high voltage is applied for protoplasts/cells/tissues, which makes transient pores in the plasma membrane which facilitates the uptake of foreign DNA.
    • Particle Gun- In this method, the foreign DNA is coated (precipitated) on to the surface of minute gold or tungsten particles (1 - 3 micrometre) and bombarded (shot) on to the target tissue or cells using a particle gun (also called as gene gun/shot gun/micro projectile gun) .

18. What is the specialty of the plant bioreactor?

  • Plant cells are cultured in specially designed “plant bioreactors” which essentially do not have a stirrer because plant cells are shear sensitive. In place of stirrer, gas is gently bubbled which provides stirring as well as meet the demand of a higher oxygen supply.

19. What is Golden Rice? In what way it is different from the normal rice?

  • Normal rice is very low in vitamin A. Prof. Ingo Potrykus and Dr. Peter Beyer developed genetically engineered rice known as Golden rice which is enriched in pro-vitamin A by introducing three genes involved in the biosynthetic pathway for carotenoid, the precursor for vitamin A. The seeds of Golden rice are yellow in color because of pro-vitamin A which is produced in the entire grain.

20. What is the name of the first genes available for genetic engineering of crop plants for pest resistance?

  • The first genes available for genetic engineering of crop plants for pest resistance were ‘cry genes’ (popularly known as Bt genes) from a bacterium Bacillus thuringensis.

Animal Biotechnology

1. Which antigen is present on T-cells which cause graft rejection during transplantation?

  • A surface antigen CD3 exposed on mature T-lymphocytes is responsible for allograft rejection.

2. How does OKT3 help in transplantation?

  • An antibody directed against CD3 surface antigen of T – cells, OKT3 (anti-CD3 Moab) removes antigen bearing cells from circulation and from the graft.

3. Which are the most commonly used enzymes for separating cells in a given tissue for culture?

  • Trypsin and collagenase

4. Which is the first drug to be produced by mammalian cell culture?

  • Tissue plasminogen Activator

5. What do you mean by cell based therapy?

  • The stem cell technology is used to replace damaged and dead cells to treat blood cancer, neuro and degenerative diseases etc. This is known as cell based therapy.

6. Name a few medically important commercial proteins produced by animal cell culture.

  • T-PA protein produced by CHO cells is used to treat heart attack. Factor VIII from CHO cells are used to treat Haemophilia A. FSH From CHO cells is used to treat fertility.

7. What is the most distinct feature of animal cell culture?

  • Animal cells can grow in simple glass and plastic containers. While growing microbial cells and plant cells, if the nutritive medium is changed and the cells are replenished with the culture medium, the cells will grow indefinitely. However, animal cells, depending on the tissue they have been isolated from can grow even in the best nutritive media to only limited generations. The animal cells in culture also exhibit contact inhibition.