Blog Post #3 – Should we clone humans?

Hello everyone!

My inquiry Question: Should we clone humans?

In my first round of research, I will be looking into what cloning is, the history of cloning, and a few animals that have been cloned!

Firstly, there are three types of cloning!

1. Reproductive cloning: Creates copies of an entire animal [1]
2. Gene cloning: Creates copies of segments of DNA or genes [1]
3. Therapeutic cloning: Creates embryonic stem cells which scientists can use for experiments to try and produce tissues to replace diseased or damaged tissues [1]

For my rounds of research, I will be focusing on reproductive cloning!

What is cloning?

Cloning is a technique used by scientists to create exact genetic copies of living things [2]. In humans, twins are natural clones [3]. Clones contain an identical set of genetic material located in the nucleus which is in the compartment that contains the chromosomes [3]. Cells from two clones have the same DNA and the same genes in the nuclei [3].

There are two methods of creating living mammal clones and both require implantation of an embryo in a uterus: “Cloning using somatic cell nuclear transfer” and “Cloning by embryo splitting” [3].

 “Cloning using somatic cell nuclear transfer”: [3]

• FIrstly, you start with the removal of the chromosomes from an egg to create an enucleated egg
• Chromosomes are then replaced with the nucleus taken from a somatic cell of the individual or the embryo to be cloned
• Egg becomes stimulated which means it may start to divide
• If the egg starts to divide, a series of cell divisions leads to form what is called a blastocyst or a preimplantation embryo
• The blastocyst is implanted into the uterus which can result in further development, sometimes resulting in the birth of an animal.
• The animal is a clone to the individual who donated their nucleus. Its nuclear DNA is inherited by only one genetic parent

“Cloning by embryo splitting”: [3]

• This method of cloning begins with in vitro (in the glass like a test tube, for instance) fertilization
• Outside of the woman’s body, a sperm and an egg will generate a zygote 
• It will then divide into two and then into four identical cells at this stage, the cells can start to separate and are allowed to develop identical blastocysts
•  These identical blastocysts will then be able to be implanted in a uterus
• However, there is a limited development potential of the cells meaning that the procedure cannot be repeated
• The embryo splitting can only create no more than four humans and only two mice
•  The DNA in the embryo splitting is contributed from two individuals who give their germ cells – the mother and father who contributed their egg and sperm.

History of cloning: 

In the 1900’s, Hans Spemann observed into blastomeres that dislocated from the early salamander embryos that were developed into normal individuals [5]. Which suggested there was no gene loss at the early stage of development [5].  

In 1901, the cloning method of transferring the nucleus of a salamander embryonic cell to an enucleated cell was a success [5]. John Gurdon did an experiment by using a technique to produce viable frogs by using a nuclear transfer from intestinal epithelium cells [5]. His work demonstrated that cell differentiation takes place without gene loss [5]. As well as if the differentiated cells are exposed to the oocyte’s cytoplasm then cellular commitment may be reversible [5]. During the 1940s to 1950s, scientists were able to clone embryos in mammals [5]. In 1962, a mature frog was produced by transferring the nucleus of intestinal cells of tadpoles into the eggs while their nucleus was removed [5]. Keith Campbell had done experiments and became successful in producing two sheep clones from an embryonic cell line [5]. 

In 1996, scientists cloned the first animal, Dolly the sheep [2]. She was cloned by using mammary gland cells that were taken from an adult sheep [2]. Dolly, the sheep’s birth was quite moving because it had proved that the nucleus of the adult cell had all the DNA necessary to give another animal life [6]. Dolly died in 2003 at age six from lung infection which is common in animals who do not go outdoors [6].

Since Dolly’s birth, scientists have been able to clone cows, cats, rabbits, horses, cats, and dogs! [4]. However, scientists have not been successful in cloning a whole human [1]. 

In my second round of research, I will look into the advantages of cloning! 

Thank you for reading my first round of research!

References:

[1] https://www.genome.gov/about-genomics/fact-sheets/Cloning-Fact-Sheet

[2] https://www.nationalgeographic.org/encyclopedia/cloning/

[3]https://www.ncbi.nlm.nih.gov/books/NBK223960/#:~:text=Cloning%20using%20somatic%20cell%20nuclear,or%20embryo%20to%20be%20cloned

[4] https://www.bbc.com/future/article/20120229-cloning-which-animals-and-when

[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3787332/

[6] https://www.scientificamerican.com/article/20-years-after-dolly-the-sheep-led-the-way-where-is-cloning-now/

https://www.geneticsandsociety.org/biopolitical-times/born-week-dolly-sheep (image)