Animals that undergo genetic alterations by changing some sequence of their DNA are called transgenic animals. The purposes of such experimentation are laudable when they contribute to the treatment of diseases, the production of medicines and the transplantation of animal organs to humans, or are simply for commercial purposes. Below we share some examples of transgenic animals.
transgenic animals
One of the most important events in the advancement of scientific research was the possibility of cloning living beings, and as far as ethics permits, only animals. The use of these at a medical and biotechnological level is practically unlimited, since there are numerous diseases that have been eradicated thanks to the experimentations carried out on these animals.
However, what is it really about? What are your advantages and disadvantages? In the following paragraphs we will share all the updated information on what transgenic animals are, what transgenesis is all about, and we will review examples of some transgenic animals that have become celebrities.
What is Transgenesis?
Transgenesis is the process by which genetic information (DNA or RNA) can be transferred from one organism to another, transforming the recipient, and all his offspring, into transgenic specimens. The genetic material is not transferred in its entirety, only one or several genes, which have been previously chosen, extracted and placed in isolation.
Definition
Transgenic animals are those in which some characteristic has been altered at the genetic level. In theory, all living beings, and therefore all animals, can be genetically manipulated. There is literature that highlights how animals such as sheep, goats, pigs, cows, rabbits, rats, mice, fish, insects, parasites and even humans have been experimented on. But the mouse was the animal that was initially used and in which all the techniques used have been successful.
The use of mice has been particularly widespread since the genetic information inserted into their cells can be easily manipulated, it is quite likely that these genes will be transmitted to offspring, they have very short life cycles and quite large litters. On the other hand, it is a small creature, easy to handle and does not get stressed enough, if we consider its physical and mental health. Finally, its genome is very similar to that of humans.
There are several methods that have been put into practice for the production of transgenic animals:
Transgenesis by Microinjection of Zygotes
Through this method, first, using hormonal treatment, a female is induced to superovulate. Then, fertilization takes place, which can be done in vitro or in vivo. Later, the fertilized eggs are removed and placed in isolation. Here the initial phase of this method would end.
In the second phase, a solution containing the DNA that we want to add to the genome is introduced into the zygotes (cells that are the product of the meeting of the ovule and the sperm naturally or through in vitro or in vivo fertilization). .
Subsequently, these already manipulated zygotes are introduced again into the mother's uterus, so that gestation occurs in a natural environment. To conclude, once the puppies have developed and have been weaned, it is verified if they have appended the transgene (foreign DNA) to their genome.
Transgenesis by Manipulation of Embryonic Cells
With this method, instead of using zygotes, the transgene is introduced into stem cells. These cells are extracted from the developing blastula (stage of embryonic development that is characterized by a single layer of cells) and are introduced into a solution that prevents the cells from being distinguished and preserved as stem cells. A posteriori, the foreign DNA is introduced, they are reimplanted again in the blastula and, this one, is reintroduced in the maternal uterus.
The offspring obtained with this method are chimeras, which means that certain cells of their body will show the gene and others will not, for example, the "sheep-cabra", the result of the chimera between sheep and goat, said animal shows parts of its body with hair and parts with wool. Through the subsequent crossing of the chimeras, it is possible to obtain individuals that will possess the transgene in their germ line, that is, as part of their ovules or sperm.
Transgenesis by Somatic Cell Transformation
This cloning is based on extracting embryonic cells from a blastula, for subsequent in vitro culture, and then inserting them into an oocyte (female germ cell) whose nucleus was previously removed. In this way, they unite in such a way that the oocyte becomes an ovum, having in its nucleus the genetic material of the original embryonic cell, and continuing its development as a zygote.
Examples of Transgenic Animals
There is a whole series of experiments on individual animals and crosses between several of them that have been carried out openly in some cases and underhanded in others for decades. Regardless of their results, such research has greatly contributed to scientific advancement.
Frogs
In 1952, the first cloning in history was made, thus laying the groundwork for the cloning of Dolly.
dolly the sheep
Famous for being the first animal cloned by means of the cell nuclear transfer method starting from an adult cell and not for being the first cloned creature, since it was not. Dolly's cloning took place in 1996.
Noto and Kaga Cows
Its cloning was carried out in Japan several thousand times, as part of the development of a project that sought to improve the quality and quantity of meat for human consumption.
The Goat Looks
This animal was cloned in 1998, being the forerunner of the engineering cattle that could generate drugs useful for humans in its body.
The Ombretta Mouflon
It was the first animal that was cloned to save a species in danger of disappearing.
The Copycat Cat
In 2001, the Genetic Savings & Clone company cloned a domestic cat for commercial purposes.
The Zhong Zhong and Hua Hua Monkeys
In 2017, they were the first apes to be cloned using the same method used on Dolly.
Sheep 15% Human
This hybrid sheep, in the future, will make it possible to use its organs to be transplanted to humans if necessary. Your liver, heart, lungs, and brain are the organs that share the most genetic material with humans.
Cow that Produces Insulin
In 2007, the company Biosidus altered the genetic structure of the cow so that it produced milk with a variety of insulin very similar to that produced by humans and required by diabetics. In this way, cows produce a molecule called insulin precursor, which, simply by adding a protein to it in the laboratory, is transformed into normal insulin.
The Goldfish or Bright Fishes
Goldfish are evidence that sometimes genetic alterations are not for the benefit of humanity but for economic purposes. The modification of these fish was initially to detect environmental contamination, but since they were not useful for this, another less ethical use was sought for them. These zebrafish are modified with a protein obtained from jellyfish that causes them to glow in white or ultraviolet light. Today they are sold as pets.
Translucent Frog
In 2007, translucent frogs were created by crossing genes from 2 varieties of Japanese frogs. Its usefulness lies in being able to investigate the effect of chemicals on your organs, the development of cancer, etc. in these animals. The skin of these amphibians is completely transparent, so vivisections are not required to know how their organs work, since they can be seen clearly through the epidermis.
Salmon That Produces More Meat
The Chinook salmon growth gene has been incorporated into this fish, which causes it to grow 200% larger than a normal salmon and more quickly. It is not yet authorized for sale or human consumption, but infertile eggs have already been exported to Canada, which is a step forward.
Pigs That Can Donate to Humans
Perhaps it's too early to say for sure that this is possible, but a South Korean team has come a long way in this field. After several attempts, they have managed to create a pig that generates an antigen that makes acceptance by the human recipient of the organ to be transplanted from the pig much more viable.
Featherless Chicken
What is sought is that, if the chickens do not have feathers, they are easier to process, which makes them cheaper and would not pollute as much. Even Israeli scientists continue to work on their prototype, since the complete absence of feathers is a difficulty when the animal requires protection from parasites or inclement weather.
Advantages and Disadvantages of Transgenic Animals
Currently, transgenesis is a highly controversial issue within the consumer population. This controversy derives particularly from the lack of knowledge about what transgenesis is, what it is used for and what legislation should regulate the methods and use of experimental animals.
To this day, those experiments in which animals in capsules were launched into space or those in which animals were made to endure physical and psychological pain, are completely prohibited. Due to issues of animal abuse and health, not only have their protection, exploitation, transport, experimentation and slaughter been regulated, but basic standards have been established for the protection of animals used for any scientific purpose, as well as in teaching and in the training requirements of the personnel who handle them.
As part of the advantages and disadvantages that have resulted from the use of transgenic animals, we can share the following:
Advantages
- It is an advance for research, from the perspective of knowledge of the genome.
- Promotes production and animal health.
- Advances in the study of both animal and human pathologies (cancer, etc.)
- Medicine production.
- Organ and tissue donations.
- Constitution of genetic banks to prevent the disappearance of species.
Disadvantages
- By altering existing species we can endanger original species.
- The presence of new proteins where there were none before can cause the appearance of allergies.
- The site in which the new gene is placed in the genome may be undefined in certain cases, so the expected results may not be such.
- Live animals are used, so it is essential to carry out an ethical review and specify how novel and relevant the result of the experiment may be.
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