Scientists have cloned an endangered horse using cells preserved for 40 years. Some think cloning could help to prevent more species from dying out. But what is cloning? And how does it work?
What are clones?
They are genetically identical individuals. The term "cloning" describes a process that produces an exact copy of a biological being. The copy – which has the same DNA as the original – is then referred to as a clone.
It may be surprising to learn that cloning takes place all the time – naturally. Some plants and single-celled organisms produce genetically identical offspring through a process called asexual reproduction. Over the past 70 years, scientists have developed various methods of cloning artificially.
How does artificial cloning work?
The simplest way to make a clone is to take a cutting from a plant and place it in compost. In a few weeks, roots will begin to sprout.
With animals, cloning is more complicated. The most successful process is known as somatic cell nuclear transfer. Scientists collect two donor cells – one is a somatic cell from the animal to be cloned. The other is an unrelated egg cell that has had its DNA removed
They then remove the nucleus from each cell, placing the DNA from the somatic cell in the empty ovum. This then grows into an embryo, and eventually into an exact copy of the original animal.
What was the first animal ever cloned?
A frog. In 1952, researchers successfully formed a new tadpole after replacing the nucleus from an egg with the nucleus from an already developing embryo. Over the following years, scientists used the same technique to create clones of mice, fish, and cattle.
In 1996, the first mammal was cloned through somatic cell nuclear transfer. Although Dolly the sheep died from health complications at the age of six, she remains one of the most famous clones of all time.
So, why is the latest clone special?
Because his somatic cell donor is dead. In fact, this Przewalski’s horse is the exact clone of a stallion that died over 20 years ago. Luckily, the cells needed to create the clone were safe in what’s known as the Frozen Zoo.
This is a laboratory at San Diego Zoo where millions of cells belonging to over a thousand endangered species are kept in suspended animation in liquid nitrogen. Kurt Benirshke founded the zoo in 1972, hoping that it would one day be able to help with conservation. This new clone widens the gene pool of the endangered species, hopefully ensuring their survival. Forty-five years on, the successful creators of the Przewalski’s foal have named him Kurt.
Could we bring back long-dead species?
Possibly! As technology improves, many scientists are working on ways to revive animals that disappeared hundreds or thousands of years ago. Teams around the world are hoping to create the first living, breathing woolly mammoth clone using remains of the ancient animal. But the plans have their critics; many worry that such animals would struggle to survive, or disrupt modern ecosystems, putting other animals and people in danger.
Will we ever clone humans?
At the moment, nobody is seriously trying to do this. Most people consider cloning humans unethical, at the very least because the cloning process has often created animals with health problems. These would be more likely to occur in a human because primates have proven especially difficult to clone.
However, some scientists are working on using cloning technology to create stem cells. These “master” cells are the basis for all the body’s organs, blood, bones etc. and could help to repair dysfunctional or injured tissue – a tremendous breakthrough if realised.
- Is it a good idea to interfere with nature, even when trying to help endangered species?
- Make your own clone by taking a cutting and replanting it. How quickly do roots begin to appear in your cloned plant?
- Asexual reproduction
- A form of reproduction that does not involve sex cells in the case of animals, or fertilisation in the case of plants.
- Somatic cell
- Any cell from a living being that is not a reproductive cell. Dolly the sheep had a somatic donor cell from a mammary gland.
- Nuclear transfer
- Nuclear means relating to a nucleus. A nuclear transfer describes the process of the nucleus being removed from the somatic cell and placed in a different cell.
- Egg cell
- In mammals, this is also known as an ovum, which comes from the Latin word for egg.
- The part of a cell containing the genetic material, including the DNA. The nucleus also controls the cell’s activities.
- Suspended animation
- At minus 196 °C, the cells slow down and stop growing, but they do not die. When thawed, they can start acting normally within 20 minutes, even if they have been frozen for decades.
- The preservation and protection of something, in this case, wildlife.
- A biological community of organisms and their physical environment.
- Mammals that include monkeys, apes, and humans. They are distinguished by having hands, feet that are similar to hands, and forward-facing eyes.