What is Human Cloning? - Definition, Pros & Cons

Lesson Transcript
Instructor: Amanda Robb

Amanda has taught high school science for over 10 years. They have a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. They also are certified in secondary special education, biology, and physics in Massachusetts.

In this lesson we'll review what cloning is. Then we'll look at the pros and cons of two types of cloning - reproductive cloning and therapeutic cloning. We'll learn some of the controversy about the use of stem cells in cloning as well as potential benefits.

What Is Cloning?

Look around you. If you're outside or in the library, you probably see other people. You'll notice there is no exact copy of you. Everyone looks different. This genetic diversity, or differences in our genes, are important to the survival of our species. When we reproduce, our genes get mixed up into the sperm and eggs, which combine to make babies that can look completely different from the parents.

However, in cloning, one organism is made that is an exact copy of another. Like photocopies from an original, clones have the exact same DNA as the organism you started with. Cloning doesn't require sexual reproduction. To create a clone, an egg is taken from a donor, and a structure called the nucleus, which holds DNA, is taken out. This blank cell is injected with DNA from the organism to be cloned. The egg is stimulated to divide and form a new organism in a surrogate mother.

Steps in cloning
cloning process

Cloning scares a lot of people who imagine armies of identical humans created in a lab; but cloning has important uses. Let's look at the pros and cons of two types of cloning: reproductive and therapeutic.

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  • 0:04 What Is Cloning?
  • 1:11 Reproductive Cloning in Humans
  • 2:15 Therapeutic Cloning in Humans
  • 4:41 Lesson Summary
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Reproductive Cloning in Humans

Reproductive cloning is the process of making an entirely new being, not just cells or tissue. Although ethical issues stand in the way of cloning full humans, other animals, like sheep, rats, cats, dogs and even monkeys have been cloned. Monkeys are the closest relative to humans out of all the animals cloned, so the birth of two successfully cloned rhesus macaque monkeys in 1997 was a big accomplishment and provides support to the idea that one day humans could be cloned.

Although highly controversial, human reproductive cloning could be beneficial to society. First, couples who are unable to conceive could still have genetically related offspring. DNA from the parents could be put into a donor egg and developed in a surrogate mother to create a cloned baby.

Reproductive cloning
reproductive cloning

However, there are serious ethical issues involved in human cloning. Cloning is an incredibly inefficient process. Many eggs need to be used before a successful clone can be made. The process of harvesting human eggs for donation is painful, lengthy and poses health risks to the donor. There is also an increased risk of miscarriage, which can be harmful to the surrogate mother.

Therapeutic Cloning in Humans

Therapeutic cloning is the use of cloned cells to develop treatments for diseases. During therapeutic cloning, a person's DNA is inserted into a stem cell, which is a special type of cell that can become any other type of cell, without a nucleus. Instead of inserting the developing cell into a surrogate mother to form a new organism, these cells are grown in a lab, where they're given specific chemicals that can differentiate the stem cells into the needed tissue.

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