What are the Basic Steps of Cloning?

Cloning is the production of independent living tissue with DNA that is an exact copy of the donor tissue. When most people think about cloning, they are thinking about reproductive cloning, which is the cloning of an entire organism. This is a complex, difficult process that often results in failure, and it consists of several very intricate steps.

  1. Isolation of the Donor Nucleus

    • The nucleus of an animal cell contains the genetic material that serves as the blueprint for that animal. In the first step of cloning, scientists puncture the cell membrane with a tiny needle and syringe and use suction to extract the cell nucleus through the needle.

    Harvest of Egg Cells

    • For mammals, which are the animals that scientists most commonly clone, egg cells are microscopic. Scientists gather these cells from adult females. Since the success rate for animal cloning is still very low, they need many of these egg cells. All egg cells used in this step are haploid, meaning they have not been fertilized with sperm. They thus contain only half of the genetic material common to the animal's cells and have not yet undergone any development.

    Removal of Egg's Nucleus

    • As the genetic material that is present in the egg cells is not what scientists want the cloned animal to have, and as having multiple nuclei in the same cell can cause many problems for the cloning process, scientists must extract the egg cell's nucleus. They do this through a method similar to the method used to isolate the donor cell's nucleus, only they discard the egg's nucleus.

    Insertion of Donor Nucleus

    • By performing an operation that is essentially the reverse of the previous step, scientists inject the original donor cell's nucleus into the egg cell. Simply doing this does not result in a cell that will start developing, though. According to the Human Genome Project, scientists must also stimulate this cell with chemicals and electricity so that it will begin the biological processes necessary for growth and development.

    Insertion into the Surrogate Mother

    • No technology currently exists that can provide the environment necessary for an animal egg to develop outside a mother's womb. For this reason, scientists must insert the prepared egg into a surrogate mother. Once this is done, the egg cell sometimes matures into a normal fetus, eventually being born as a new organism with genetic characteristics identical to those of the donor.