Sunday, January 25, 2009

Issues on Animal/Human Cloning Difficulties and Challenges

Cloning:                                                                                                               By Bishnu Marasini
       The word cloning is derived from the Greek word ‘clone’ which means twig i.e. a group of identical entities. It is the process of making a genetically identical organism through non-sexual means (even growing a plant from cutting is a type of cloning). Most natural cloning occurs in those species which produce their descendents asexually e.g. bacteria, some fungi, Bermuda grass by means of runner stem etc. Animal cloning has been the subject of scientific experiment and the ‘Dolly’ is the first success. Here is only the cloning of human and animal is briefed.
             In 1885 Weishman put a theory stating that genetic information of a cell diminishes as the cell difference. In 1902, Hans S, split a two celled salamander embryo in two leading two adult salamanders this disproves Welshman’s hypothesis. In 1952 Robert B and Thomes JK cloned northern leopard frog using a method of nuclear transfer. A British biologist Handane JBS, in 1963 credited to have coined the term ‘clone’. Louis Jay Brown, the first child conceived through in vitro fertilization (IVF) (test-tube baby) was born in 25th July 1978. Ian W & Keith C in 23rd Feb. 1997 at Roslin Institute in Scotland announced the birth of ‘Dolly’, the first successful cloned animal. Again they created ‘Polly’ in June 1997 a lamb which was cloned from adult skin cells that was genetically altered to contain a human gene. Similarly, the birth of the first clone of an endangered animal, a baby bull ‘gaur’ named Noah was announced in 8th Jan 2001. The ‘Dolly’ was dead in 14th Feb 2003 due to progressive lung disease.

i) Gaining of Oocytes/ egg cells: Various hormones like human menopausal gonadotropin (hMG), clomiphene, follicle stimulating hormone (FSH) is given for 5-10 days to the mature female of same species which is to be cloned.

ii) Enucleating of eggs/oocytes/somatic cell of donor: This is achieved by centrifuging cytochalastin-B treated cells such that nuclei detached from the eggs at the bottom of the tube leaving enucleated eggs in the supernatant. Cells/tissues taken from different organs like skin, bone, blood, mammary gland) of donor is cultured in petri-dish and single cell is isolated & nucleus is separated from cells which is ready to be injected in egg cells/oocytes.

iii) Injection of nucleus from donor (which is to be cloned)
  1. Using microinjection technique: The egg cells or oocytes is first immobilized by applying mild suction to the large blunt holding pipette & nucleus or DNA is then injected through the sharp end of a narrow glass micro needle.
  2. Isolated chromosomes with whole cells after co-precipitation with calcium phosphate.
  3. Fusion with electrical pulses.
iv) Culture: Thus the egg cells/oocytes injected with foreign nucleus (of donor) is cultured in vitro (2-8 cell stage) for certain period of time (48-72 hour) and then transferred into uterus.

v) Embryo transfer: embryo transfer in uterus of surrogate mother is done with the help of sonographer by using a Teflon catheter which is non sticky & done with 10 µl – 1 ml culture media. The surrogate mother is advised to rest for 24 hours and return in normal work after 48 hours.

Possible Uses:
  1. It is a good solution for increased infertility rate.
  2. To replace a child who has been lost by disease or accident.
  3. The duplication of individuals with particular talents or ability or importance.
  4. To conserve biodiversity including rare breeds.
  5. Non reproductive use of cloning (research cloning) is used for studying genetic change in cells derived from patients with conditions such as Alzheimer’s disease, Parkinson’s disease, diabetics etc.
  6. Making new animal models for human diseases, especially genetic diseases & for producing animals for use in xenotransplantation.
  7. The cloned animals will secret valuable recombinant protein and pharmaceuticals into their milk &/or blood &/or urine which can be used for extraction of these drugs; e.g. in sheep, ovine β-lactoglobulin gene promoter was fused in human a antitrypsin (hα,AT) gene which later produce hα,AT protein in milk used to treat the disease emphysema and cystic fibrosis.
Issues Difficulties and Challenges:
                 Ethical issue may arise regarding animals and human beings. There is no support in human cloning from the scientific community, religious community and other community and banned in various European countries and USA. If human cloning is allowed, only the rich may be benefited because of its cost. Also the surrogate mother may claim the child.
                 Success rate of cloning is very low, if succeed abnormal growth and/or disease may be seen because the cloned animal are vulnerable to be infected e.g. Dolly was suffered from arthritis and lung disease. Human cloning is more difficult than sheep or cattle because the cells of human embryos start producing proteins at relatively early stages. Cloning experiment in Japan show damage to immune systems, risks of death from pneumonia, liver failure, spontaneous abortion and abnormal births.
                Cloning procedure like research cloning seems to be very beneficial to human beings but their use and proper monitoring is essential and more and more people must be benefited.

Published in
Marasini, BP (2008), Microcosm, Vol. 3 No. 1