Cloning Objectives: Be able to… Describe the process of embryo transplants and adult cell cloning in animals Explain the advantages and disadvantages of cloning techniques

Cloning What do you already know?

Clones… Definition of a clone? A clone is an organism that is genetically identical to it’s parent It is more difficult to clone animals than plants, but two methods that can be used are embryo transplants and adult cell cloning

Identical twins Identical twins are natural clones They share the same DNA, so any differences are due to environmental factors

Embryo transplants A fertilised egg begins dividing, the cells are split before they become specialised The cells are implanted into surrogates Cattle farmers use embryo transplants to produce calves with characteristics of the best bull and best cow - all the calves produced are clones of each other Cattle with high milk yield or lots of meat can be bred.

Embryo transplants

Adult cell cloning The genetic material of an adult is used to make a clone of that adult The genetic material is put into an empty egg (from a different adult) The cell starts dividing and becomes an embryo Dolly the sheep was the first mammal to be cloned from the DNA of an adult Since then cows, dogs, cats, goats and pigs have been cloned. In 1952, the first animal cloned was a tadpole. Dolly and her first-born lamb, Bonnie

Cloning Dolly- NY Times kE kE

Reproductive cloning-Dolly the sheep Dolly was created by a reproductive cloning process called “somatic cell nuclear transfer” (SCNT). – In this process the genetic material from a Somatic cell – (any type – skin, blood, etc) is transferred to an egg that has had its nucleus removed. It is then stimulated to produce an embryo by chemicals or electric current. Then put into a surrogate mother. A somatic cell ( all cells of the body except the sperm and egg cell) is used because it has a full set of chromosomes. Sperm and egg cells only have one set of chromosomes.

How Dolly was cloned…

The advantages and disadvantages of animal cloning  1. Can quickly make copies with useful characteristics 1. Short life spans 2. The original animal can make eggs all year round 2. Immoral 3. Extinct or endangered species can be repopulated through cloning. 3. Many eggs may be needed to make one clone – takes time and money Deextinction

Therapeutic cloning – is the production of cloned cells for the sole purpose of harvesting stem cells. –SCNT is performed but the resulting zygote is not allowed to grow past the blastula stage. In this manner, a patient’s skin cell could later be induced to grow new tissue to replace damaged heart, nervous, or muscle cells.

What is a Stem Cell? Stem cells are unspecialized cells that have the potential to differentiate—to become specialized in structure and function—into a wide variety of cell types. In early embryonic development, stem cells produce every tissue in the body. Evidence indicates that stem cells also are found in adults. Stem cells in the bone marrow, for example, produce more than a dozen types of blood cells, replacing those lost due to normal wear and tear.

Sources of Stem Cells Human embryonic stem cells were first isolated in Many scientists are now experimenting with ways to produce such cells by transferring adult cell nuclei into the cytoplasms of egg cells. However, since these techniques use or produce early human embryos, they also raise serious moral and ethical questions. Because of such issues, embryonic stem cell research is highly controversial.

In 2006, Canada enacted a law permitting research on discarded embryos from in vitro fertilization procedures. However, it prohibits the creation of human embryos for research. The field of embryonic stem cell research has been highly controversial, because in most cases, the research process involves destroying the embryo, typically four or five days old, after removing stem cells. In the US: Legislation passed in 1996 prohibits the use of taxpayer dollars in the creation or destruction of human embryos "for research purposes." Private money had been used to gather batches of the developing cells at U.S.-run labs. That congressional ban had been renewed annually.

Researchers have also found that nerve, muscle, and liver cells sometimes can be grown from adult stem cells isolated from the bone marrow and other tissues in the body. Experiments such as these, although still in the early stages of development, may usher in a new era of therapy in which replacement tissue is grown from a person's own stem cells.

Stem Cells in Medicine Although your body produces billions of new cells every day, it is not always able to produce the right kind of cell to replace those damaged by injury or disease. For example, the body is not able to produce new neurons to repair serious spinal cord injuries, such as those that cause paralysis. Because of this, at present, there is no way for doctors to restore movement and feeling to people who are paralyzed.

Stem cells may be the perfect solution to this problem. Recently, researchers have found that implants of stem cells can reverse the effects of brain injuries in mice. There is hope that the same will hold true for humans and that stem cells might be used to reverse brain and spinal cord injuries. It also may be possible to use stem cells to grow new liver tissue, to replace heart valves, and to reverse the effects of diabetes.

Exam question Answers: 1 a) The genetic material came from only one parent - the nucleus was removed from the egg cell b) i) Gender = male Face colour = white ii) The genetic material came from the white- faced male only

Dolly the sheep