Here is a compilation of essays on ‘Transgenesis in Animals’ for class 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Transgenesis in Animals’ especially written for school and college students.
Essay on Transgenesis in Animals
Essay Contents:
- Essay on the Introduction to Transgenesis
- Essay on the Mechanism of Transgenesis in Animals
- Essay on the Significance of Transgenesis
Essay # 1. Introduction to Transgenesis:
Conventional animal husbandry involves the proper feeding, caring, management and breeding methods for the increased production of their yield which may be in the form of meat, milk, eggs, etc. In animal husbandry, selective breeding aims to increase the frequency of desired genes and the desired phenotype. For many farm animals, the conventional breeding has already achieved high yielding animals but by this procedure, it seems that the productivity would soon be approaching a plateau.
To sustain an ever increasing world population, new methods must be developed to meet this increasing demand for animal products. Secondly, selective breeding is a painfully slow process and, especially with larger animals with long gestation period, can take many years to establish desired phenotypic changes.
The advent of technology of transgenesis also called transfection and its application to animal breeding programmes may greatly increase the speed and range of selective breeding. The transgenesis involves the transfer of desired isolated gene or gene fragments or individual chromosome or chromosomal fragments, or isolated nuclei from one organism to another organism.
The first recorded examples of the transfer of a foreign gene into an animal by recombinant DNA technology was the insertion and expression of a rat gene for growth hormone (rGH) into the mouse metallothionein (mMT) gene in 1882. The subsequent progeny were all much larger than, the parents and the transgenic mouse was called “super mouse” (Fig. 12.11). Since then, many transgenic animals including cattie, goats, pigs, rabbits, chickens and fish have been produced (Table 12.2).
About 95 % of the existing transgenic animals are mice.
Essay # 2. Mechanism of Transgenesis in Animals:
Transgenesis involved a number of methods like:
1. Transfer of whole nucleus from a somatic cell of a superior donor into the enucleated egg of recipient animal.
2. Transfer of a part of dissected embryo into the enucleated unfertilized egg.
3. Transfer of a chromosome or chromosomal fragments.
4. DNA microinjection technique.
5. Gene targeting using embryonic stem cells.
Frequency of Success of Transgenesis:
Now the transgenic pigs, sheep and cattle have been produced, although the frequency of success is only about 1% compared to 2-5% in mice while successful fish transgenics can be as high as 70 %.
Essay # 3. Significance of Transgenesis:
1. Role of Transgenesis in Molecular Farming:
Molecular farming involves the extraction of useful proteins and drugs from the milk, food and urine of hansgenic animals which may be used as bioreactors e.g:
(i) Transgenic goats with LAtPA protein were produced by microinjecting murine whey acid promotor (WAP) carrying a c-DNA with LAtPA protein coding gene. The LAtPA protein dissolves the blood clot and is useful for treating coronary thrombosis.
(ii) Transgenic sheep with human antihaemophillic factor IX gene was produced with the help of BLG-gene (β-Lactoglobulin gene), which acts as vector gene Transgenic ewes secrete human factor IX in their milk.
(iii) Transgenic sheep having human α1 antitrypsin gene (hα1 AT) was produced with the help of ovine β- lactoglobulin gene promotor. Transgenic ewes produce h α1 AT protein in their milk and can be used against the emphysema.
Thus by transgenesis the animals are genetically modified in such a way that they start acting bioreactors
producing useful products in abundance and continuously.
2. Study of Diseases and Gene Therapy.
Many transgenic animals help us to understand the following facts:
(i) How do genes contribute to the development of disease?
(ii) These act as models for human diseases like cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer’s disease, etc., and their possible new methods of their treatment.
(iii) Transfections of cultured mammalian cells have been used extensively for detecting the cancer genes (oncogenes) and their gene therapy. In these retroviruses, adeno- associated virus (AAVs) and naked DNA have been used as vectors and gene therapy.
(iv) In 1991, the transgenic cow with a bovine alpha- Si casein promotor driving a c-DNA was produced. This foreign gene encodes for the lactoferrin (a iron- binding protein) which has the antibacterial properties.
3. Increased Production of Biological Products:
(i) Transgenic sheep with genes like cysE and cys M (coding for two enzymes—serine acetyl transferase and o-acetyl serine sulphhydrylase) have been produced. In the transgenic sheep, wool production was found to much more than the non-transgenic sheep because these two enzymes are essential for the biosynthesis of the amino acids involved in the formation of wool.
(ii) In 1985, the transgenic fishes of many species like common carp, catfish, goldfish, salmon, Tilapia, rainbow trout and zebra fish have been produced by microinjection of genes coding for rat or human growth hormone (rGH or hGH). It was found that transgenic fish with hGH gene was found to be twice in size than the non- transgenic fish.
(iii) In 1997, first transgenic cow, named Rosie, with human alpha-lactalbumin gene was produced. The milk of transgenic cow contained about 2.4 grams of human protein per litre of milk and was found to be more nutritionally balanced product for human babies than that of natural cow milk. Such human milk proteins can be extracted and used pharmaceutically.
4. For Study of Normal Physiology and Development.
Transgenic animals have been successfully utilized to understand:
(i) Mechanism of regulation of genes.
(ii) Mode of effects of genes on the normal functions of the body and its development e.g. study of biological role of insulin-like growth factor in regulating the body’s growth.
5. Vaccine Safety Testing:
Transgenic mice are first to be used as laboratory animals to test the efficacy of a newly discovered vaccine before it is used on human beings e.g. polio vaccine. If such vaccines are found satisfactory and reliable on mice, then these are tested on the monkeys much closely related to man.
6. Chemical Safety Testing:
For this transgenic animals with foreign genes are produced so that the transgenic animals become more sensitive to the toxic chemicals of them, the non-transgenic animals. Then these animals are exposed to toxic chemicals and their effects are observed. The time required to obtain the results is less.
So contrary to some popular view points, transgenic animal studies are not about producing animal monsters but rather introducing specific and economically significant traits into livestock that will have benefits to mankind. These encouraging results have made transfection and production of transgenic animals a fascinating thrust of research.