Scientific Foundations

Cells are the building blocks of an animal's body. All parts of an animal, including skin, hair, and bone are made of cells. In the nucleus (the part of the cell containing the information needed for cell reproduction) of each cell is deoxyribonucleic acid (DNA). DNA, also referred to as genes, contains instructions that determine the physical traits of a living thing. Animals, just like humans, inherit half of their DNA from their mother, and half from their father.

In nature, when a sperm from a male animal fertilizes an egg from a female, the fertilized egg begins to divide into multiple cells. After a few days, it becomes an embryo (an animal or human in the earliest

stages of development). That embryo implants in the female's uterus (a hollow organ in the female's body in which the fetus grows). Sometimes a fertilized egg divides into two separate embryos that are genetically the same. These are called identical twins.

When scientists clone an animal, they put the nucleus from an adult animal cell into an unfertilized egg that has had its own nucleus removed. They stimulate the egg and genetic material with an electric shock, causing them to combine and begin dividing.

How mammals are cloned. An egg donor is implanted with the nucleus of a donor cell. Afterthe egg develops, it becomes a clone of the nucleus donor. Illustration by GGS Inc.

Animal cloning

How mammals are cloned

Egg Donor

Nucleus Donor

Egg Donor

Remove and discard nucleus

Nucleus-free egg

Nucleus Donor

Inject one nucleus into egg

Skin cells in culture

Skin cells in culture

Nucleus-free egg

Remove nuclei

Inject one nucleus into egg

Remove nuclei

Eight-cell embryo develops and is implanted into surrogate mother

Surrogate Mother

Eight-cell embryo develops and is implanted into surrogate mother

Cloned Pig

Surrogate Mother

Cloned Pig

The embryo that results from this division is implanted into a surrogate (a female that carries another animal's genetic offspring) animal of the same species.

Dolly was born on July 5,1996 at the Roslin Institute in Scotland. By all appearances, she looked and acted like a normal sheep, but she was not normal. She was a clone, the first cloned sheep successfully born. Dolly grew up and gave birth to several lambs, but she suffered from premature aging. This disease caused her body to have symptoms of old age while she was still young. She eventually developed arthritis (a disease causing swelling and pain in the joints) and lung disease. Scientists believed her health problems may have been related to the cloning process. Dolly was put to sleep in February 2003 at the age of six.

Arthritis Joint Pain

Arthritis Joint Pain

Arthritis is a general term which is commonly associated with a number of painful conditions affecting the joints and bones. The term arthritis literally translates to joint inflammation.

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