Biology · Chapter 2
Study notes aligned to the official NEB syllabus.
Applied biology covers medical and agricultural techniques that apply biological principles to human welfare, including tissue/organ transplantation, test tube baby technique, amniocentesis, transgenic animals, and poultry farming.
When a person is seriously injured or an organ is damaged, the damaged tissue or organ is replaced with a healthier, functional tissue or organ. This medical procedure is called transplantation. The tissue or organ that is transplanted is called a transplant or graft.
The first heart transplant was performed in 1967, and involves a receiver and a donor organ.
Based on the genetic relationship between donor and receiver, transplantation is of the following types:
(a) Autografting When a graft is taken from one site and transplanted to another site in the same person, it is called autografting. Skin grafting is an example. This type does not have a chance of rejection.
(b) Isografting Grafting between genetically identical members of a species is called isografting. It also does not have a chance of rejection. Kidney transplantation between twins is an example.
(c) Allografting (or Homografting) When grafting is done between members of the same species, it is called allografting/homografting. In this case the chance of rejection is higher because the donor and receiver have different genetic makeup. Blood transfusion is an example.
(d) Xenografting (or Heterografting) When grafting is done between members of different species, it is called xenografting. In this case, the chance of rejection is maximum. To reduce rejection, the donor species is genetically modified. The transplantation of a genetically modified pig's valve to replace a dysfunctional human valve is an example.
In humans, fertilization is internal, and this kind of fertilization is called in vivo fertilization. When couples have disorders in their reproductive parts, they cannot conceive a baby. The medical assistance which helps such couples to have their own babies is called the in vitro fertilization (IVF) technique. In this method, fertilization is performed out of the body, in a test tube. Therefore, the in vitro fertilization technique is called the test tube baby technique.
Fertilization normally occurs in the ampulla of the fallopian tube and also requires sperm mobility. To be a fertile male, the sperm count must be 15 to 20 million sperms per ml of semen; a count of less than 15 to 20 million per ml means fertilization does not occur (low sperm count and low sperm motility, as stated in the source).
This technique is applied only when other methods have failed, because it is expensive, time consuming, and has a low success rate. It is performed when the ovary, uterus, or fallopian tube is blocked, or when there is a disorder such as low sperm count or poor sperm motility.
The first test tube baby of the world was Louise Joy Brown, born on 28th July 1978 with the help of doctors Patrick Steptoe and Robert Edwards. The first test tube baby of Nepal was Om Madi Tamang (as stated in the source), born on 3rd March 2005 in Om Hospital.