By: Raghav Bahukhandi
It’s June, 2012, and Thelma, the python of Louisville zoo in Kentucky, USA, has just given birth to six female pythons. Nothing unusual about that right? Except Thelma had never been near a male python. Recent studies published in the biological journal of Linnean society revealed that Thelma was, in fact, the sole parent. In this particular case, Thelma’s two eggs (female sex cells), which were haploid, had fused together to make up for the missing amount of chromosomes. This type of fatherless reproduction that takes place in animals is known as parthenogenesis.
Usually, having two parents provides variation in the child which is necessary for the survival of species, but in the case of parthenogenesis, all the chromosomes belong to a single parent. So, in a way, the newly born child is half a clone of the parent. However, scientists say that these newly born snakes wouldn’t be able to survive in a real jungle because they are highly inbred and fragile. Thelma wasn’t the first animal to reproduce using parthenogenesis, but it was the first such case in the species.
Cloning is the process of producing individuals with identical or virtually identical DNA, and it happens all the time in nature. Many microorganisms such as the Hydra and Planaria can create clones of themselves, but parthenogenesis is important as it is a method by which animals who use sexual reproduction can create clones, giving some insight into cloning for humans.
Cloning in Humans
Natural cloning happens in humans as well, although it is quite rare. It happens when an embryo splits into two, and both the embryos have genetic information that is somewhat similar. This is how twins are born.
Artificial cloning, or reproductive cloning to be more precise, is done by a process known as Somatic Cell Nuclear Transfer (SCNT). In this process, the nucleus of a mature somatic cell (any cell except the sex cells, which have half the number of chromosomes) of the donor animal is transferred to an egg cell whose nucleus has already been removed. This transfer takes place in one of two ways: either the nucleus is extracted from the somatic cell with a needle and then injected into the empty cell, or the somatic cell and the egg are fused together by the use of an electric shock. Then the cell is allowed to develop into an embryo in a test tube and is later transferred to the womb of the female.
After some time, the female gives birth to an animal that is genetically similar to the person who donated the somatic cell. The first animal to be born in this way was Dolly the sheep in 1996.
It is also important to note that no biochemical reaction is 100% accurate, so the clone is similar but very slightly different from the original. The knowledge about cloning animals is not by any means new. In fact, humans have been experimenting with the technique of cloning for about 50 years... which begs the question, why haven’t we cloned humans yet? Well, there are a few technological drawbacks and concerns about how ethical this process is.
Cloning in primates is much harder as compared to other mammals and even reptiles. The reason for this is that two proteins necessary for cell division are very close to the chromosomes, so during the removal of the nucleus, these proteins can also get removed, which hinders cell division.
Apart from that, some of the dyes and UV lights that are used in this process can damage the cell and stop it from growing.
The entire process is pretty inefficient as well. Dolly the sheep was the only embryo that was born alive out of a total of 277 embryos.
The risks associated with reproductive cloning in humans introduces a high likelihood of embryonic loss of life. It is due to this reason that it is condemned universally.
Concerns about eugenics, the once-popular notion that the human species could be improved through the selection of people with “desired traits”, have also been raised. Apart from these, there are also psychological and social risks associated with cloning.
When it comes to human cloning, many questions still remain unanswered. Is the clone inferior to the person whose somatic cells were used? If they are eating together, then who gets the last slice of pizza? Will clones be treated like normal humans? It is due to these reasons that nobody has cloned humans or even intended to.
What did you learn?
Q1) What is parthenogenesis?
Parthenogenesis is a type of fatherless reproduction in which the growth and development of an embryo occurs without fertilization by sperm.
Q2) What is cloning?
Cloning is the process of producing individuals with identical or virtually identical DNA.
Q3) What is Somatic Cell Nucleus Transfer (SCNT)?
It is a process in which the nucleus of a mature somatic cell of the donor animal is transferred to an egg cell whose nucleus has already been removed.
Q4) Ethical concerns related to human cloning:
The risks associated with reproductive cloning in humans introduces a high likelihood of embryonic loss of life. Concerns about eugenics, the once-popular notion that the human species could be improved through the selection of people with “desired traits”, have also been raised. Apart from these, there are also psychological and social risks associated with cloning.