1. Production of insulin by recombinant DNA technology started in the late 1970s.
2. This technique involved in the insertion of human insulin gene on the plasmids of E. Coli. The polypeptide chains are synthesized as a precursor called pre-proinsulin as it contains A and B segments linked by a third chain (c) and preceded by a leader sequence.
3. The leader sequence is removed after translation and 'c' chain is excised, leaving the A and B polypeptide chains.
4. Insulin was the first ever pharmaceutical product of r-DNA, technology.

Advantages
1. Offers benefits for clinical traits and medical research.
2. It can help in the production of help in the production of proteins and drugs in the field of medicine.
3. Aids in stem cell research
4. Animal cloning could help to save endangered species.
Disadvantages
1. In animal and human activities, it as a threat to biodiversity saying that this alters evolution which will have an impact on populations and ecosystem.
2. The process is tedious and very expensive.
3. It can cause animals to suffer
4. Reports show that animal surrogates were manifesting adverse outcomes and cloned animals were affected with disease and have high mortality rate.
5. It might compromises human health through consumption of cloned animal meat.
6. Cloned animals age faster than normal animals and are less healthy than the parent organisms as discovered in Dolly.
7. Cloning can lead to occurrence of genetic disorders in animals.
8. More than 90% of cloning attempts fail to produce a viable offspring.

(i) Stem cells are undifferentiated cells found in most of the multicellular animals. 
(ii) These cells maintain their undifferentiated state even after undergoing repeated mitotic divisions.
(iii) Stem cells research has the potential to revolutionize the future of medicine with the ability to regenerate damaged and diseased organs.
(iv) Stem cell research has the potential to revolutionize the future of medicine with the ability to regenerate damaged and diseased organs.
(v) They are capable of self renewal and exhibit 'cellular potency'.
(vi) They can differentiate into all types of cells that are derived from any of the three germ layers ecto, endo and mesoderms.
(vii) In mammals there are two types of stem cells namely embryonic stem cells & adult stem cells (ES).
(viii) ES are pleuripotent and can produce the three primary germ layers ectoderm, Mesoderm and endoderm.
(ix) Embryonic stem cells are multipotent stem cells that can differentiate into a number of type of cells.
(x) ES cells are isolated from the epiblast tissue of the inner cell mass of a blastocyst.
(xi) When stimulated ES can develop into more than 200 cells Qpes of the adult body.
(xii) ES cells are immortal i.. e they can proliferate in a sterile culture medium and maintain their undifferentiated state.
(xiii) Adult stem cells are found in various tissues of children as well as adults.
(xiv) An adult stem cell or somatic stem cell can divide and create another cell similar to it.
(xv) Most of the adult stem cells are multipotent and can act as a repair system of the body and replenishing adult tissues.
(xvi) The red bone marrow is a rich source of adult stem cells.
(xvii) The most important and potential application of human stem cells is the generation of cells and tissues that could be used for cell based therapies.
(xviii) Human stem cells could be used to test new drugs.

1. A patient is suffering from ADA deficiency can be caused by using "gene therapy''.
2. Gene therapy is a correction of a genetic defect that has been diagnosed in a child embryo.
3. ADA enzyme is crucial fol the immune system to function.
4. Deletion of the gene for adenosine deaminase results into ADA deficiency.
5. In some children, ADA deficiency can be cured by bone. Marrow transplantation While in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches is that they are not completely curative.
6. It may recurrent in nature as in the process of gene therapy, Lymphocytes used are found not to be immortal in nature and the patient requires a periodic infusion of such genetically engineered lymphocytes.
7. For permanent cure, gene isolated from the bone-marrow-cells producing ADA is introduced into cells at early embryonic stages.

1. The human insulin is synthesized by the \(\beta\) cells of Islets of Langerhans in the pancreas. It is formed of 51 amino acids which are arranged in two polypeptide chains, A and B. The polypeptide chain A has 21 amino acids while the polypeptide chain B has 30 amino acids.
2. In the early years, insulin isolated and purified from the pancreas of pigs and cows was used to treat diabetic patients. Due to minor differences in the structure of the animal Insulin as compared allergic reactions in some diabetic patients.

1. In 1997, Rosie, the first transgenic cow produced human protein enriched milk, which contained the human alpha lactalbumin.
2. Alpha lactalbumin is a protein composed of 123 amino acidic and 4 disulphide bridges, with a molecular weight of 14178 Da.
3. In human milk, & lactalbumin is the most abundant protein comprising 25% of total protein found in human milk.
4. It is synthesized by the mammary glands & lactalbumin binds calcium and zinc ions and possesses bactericidal antitumor activities.