One of the most important facts in scientific progress was the possibility of cloning animals The medical and biotechnological uses are almost innumerable, since There are many diseases that have been eradicated thanks to these animals. However, what is it really? What advantages and disadvantages does it have?
In this article on our site we will explain what transgenic animals are, what transgenesis consists of and we will show you examples of some animals famous transgenics.
What is transgenesis?
Transgenesis is the procedure through which genetic information (DNA or RNA) is transferred from one organism to another, becoming the second, and all its descendants, in transgenic organisms The complete genetic material is not transferred, only one or several genes, which have been previously selected, extracted and isolated.
Definition of transgenic animals
Transgenic animals are those that have had some characteristic genetically modified.
Theoretically, all living beings, and therefore all animals, can be genetically manipulated. There is literature where animals such as sheep, goats, pigs, cows, rabbits, rats, mice, fish, insects, parasites and even humans have been used. But it has been the mouse the animal that was used in the first place and in which all the techniques used have been successful.
The use of mice has been especially widespread because new genetic information can be easily manipulated within their cells, these genes are easily transmitted to offspring, they have very short life cycles and very numerous litters. On the other hand, it is a small animal, easy to handle and not very stressful, if you take into account its physical and mental he alth. Finally, its genome is very similar to that of the human being.
There are several techniques to produce transgenic animals:
Transgenesis by microinjection of zygotes
Using this technique, firstly, using a hormonal treatment, a female is superovulated. Then, fertilization is performed, which can be done in vitro or in vivo. The fertilized eggs are then removed and isolated. Here would conclude the first phase of the technique.
In a second phase, the zygotes (cells resulting from the union of the egg and a sperm naturally or through in vitro or in vivo fertilization) are introduced bymicroinjection a solution containing the DNA we want to add to the genome.
Next, these already manipulated zygotes are reintroduced into the mother's uterus, so that gestation takes place in a medium natural. Finally, once the puppies have grown and been weaned, they check if they have incorporated the transgene (foreign DNA) into their genome.
Transgenesis by manipulation of embryonic cells
In this technique, instead of using zygotes, the transgene is introduced into stem cells These cells are extracted from the blastula (phase of embryonic development characterized by a single layer of cells) in development and are introduced into a solution that prevents the cells from differentiating and remaining as stem cells. Subsequently, the foreign DNA is introduced, they are re-implanted in the blastula and the latter is reintroduced into the maternal uterus.
The offspring obtained with this technique are chimeras, this means that some cells in their body will express the gene and others will not, for example, the "sheep goat" , a chimera between sheep and goat, the resulting animal has body parts with hair and part with wool. Through the subsequent crossing of the chimeras, individuals are obtained who will have the transgene in their germ line, that is, in their ovules or spermatozoa.
Transgenesis by somatic cell transformation and nuclear transfer or cloning
Cloning consists of extracting embryonic cells from a blastula, growing them in vitro, and then inserting them into an oocyte (germ cell female) from which the nucleus has been removed. Thus, they fuse in such a way that the oocyte becomes an ovum having in the nucleus the genetic material of the original embryonic cell, and continuing its development as a zygote.
Examples of transgenic animals
- Frogs: in 1952 the first cloning in history was carried out. It was the basis for cloning Dolly.
- The Dolly Sheep: It is famous for being the first animal cloned using the cell nuclear transfer technique from an adult cell and not for being the first cloned animal, because it was not. Dolly was cloned in 1996.
- Noto and Kaga cows: they were cloned in Japan several thousand times, as part of a project that sought to improve the quality and quantity of meat for human consumption.
- The Mira Goat: This goat, cloned in 1998, was the precursor of the engineered cattle that could produce drugs in its body useful for the human being.
- The Ombretta mouflon: the first cloned animal to save an endangered species.
- The copycat cat: In 2001, the company Genetic Savings & Clone cloned a domestic cat with for commercial purposes.
- Zhong Zhong and Hua Hua monkeys: first cloned primates with the technique used with Dolly, in 2017.
Transgenic animals: advantages and disadvantages
Currently, transgenesis is a very controversial topic for the consumer population, this controversy stems above all from the lack of knowledge about what transgenesis is. transgenesis, what are its uses and what legislation regulates the technique and the use of experimental animals.
Today, those experiments in which animals were placed in capsules to launch them into space or those in which animals suffered physical and psychological pain are Strictly prohibitedthanks to Law 8/2003, of April 24, on animal he alth, Law 32/2007, of November 7, for the care of animals, in their exploitation, transport, experimentation and sacrifice, to Royal Decree 53/2013, of February 1, which establishes the basic applicable standards for the protection of animals used in experimentation and other scientific purposes, including teaching, and to Order ECC/566/2015, of March 20, which establishes the training requirements to be met by personnel handling animals used, bred or supplied for experimentation and other scientific purposes, including teaching.
Among the advantages and disadvantages obtained from the use of transgenic animals we find:
Advantage
- Improvement for research, from the point of view of knowledge of the genome.
- Benefits for animal production and he alth.
- Advances in studies of animal and human diseases, such as cancer.
- Drug production.
- Organ and tissue donation.
- Creation of genetic banks to prevent the extinction of species.
Cons
- By modifying existing species we can put native species at risk.
- The expression of new proteins where they did not exist before can cause the appearance of allergies.
- The place where the new gene is placed in the genome may be undetermined in some cases, so the expected results may be wrong.
- Live animals are used, so it is essential to conduct an ethical review and determine how novel and important the results of the experiment may be.
