Animal cloning is most commonly achieved through a process called Somatic Cell Nucleus Transfer (SCNT).
Understanding Somatic Cell Nucleus Transfer (SCNT)
This technique creates a genetic copy of an animal by combining components from two different cells. As stated in the reference, this most commonly involves a technique known as somatic cell nucleus transfer (SCNT). A genetic copy of an animal is produced by replacing the nucleus of an unfertilised ovum (egg cell) with the nucleus of a body (somatic) cell from the animal to form an embryo.
Here's a breakdown of the key steps involved in SCNT:
The Process of SCNT
The process essentially involves taking the genetic material from a regular body cell of the animal you want to clone and placing it into an egg cell that has had its own nucleus (and thus, its own genetic material) removed.
Let's look at the steps:
| Step | Description |
|---|---|
| 1. Donor Somatic Cell Collection | A somatic cell (any body cell other than a reproductive cell), such as a skin cell or muscle cell, is collected from the animal to be cloned. This cell contains the complete genetic blueprint (DNA) of the animal. |
| 2. Enucleation of Egg Cell | An unfertilised ovum (egg cell) is obtained from a donor animal of the same species. The nucleus of this egg cell, which contains its original genetic material, is carefully removed or inactivated. This creates an "enucleated" egg cell. |
| 3. Nucleus Transfer | The nucleus from the donor somatic cell is then transferred into the enucleated egg cell. This can be done using various methods, such as microinjection or electrical pulses that help fuse the cells. |
| 4. Activation | The reconstructed egg cell, now containing the somatic cell nucleus, is stimulated (often using electrical pulses or chemicals) to start dividing and developing as if it had been fertilised naturally. |
| 5. Embryo Culture | The resulting embryo is cultured in a laboratory for a few days until it reaches a certain stage of development (e.g., blastocyst stage). |
| 6. Embryo Transfer | The developed embryo is then transferred into the uterus of a surrogate mother animal, who carries the pregnancy to term. |
The resulting offspring is a genetic copy of the animal from which the somatic cell nucleus was taken. While the nuclear DNA is identical to the donor animal, factors like mitochondrial DNA (from the egg cell) and environmental influences during development can lead to some differences between the clone and the original animal.
This sophisticated technique has allowed for the cloning of various animal species, including sheep (like Dolly, the first mammal cloned from an adult somatic cell), cows, pigs, horses, and even pets like cats and dogs.
