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HOME > Review > Good-bye to Dolly the cloned Sheep
Good-bye to Dolly the Cloned Sheep

Good-bye to Dolly
Dolly's life was ended at the age of 6 (about half the life expectancy of her breed) when a veterinarian confirmed she had a progressive lung disease. Dolly was born in Edinburgh Scotland on July 5th, 1996. As the first mammal cloned by nuclear transfer Dolly instantly created a heated debate on the need and the ethics of cloning mammals and specifically, humans.

Why do it?
Animals with human genes could be used to produce hormones or other biological products to treat human diseases. Production methods for these protien based treatments (such as G-CSF) are very expensive and drive up the cost of healthcare. The only thing I can't figure out is how they would get the protein to be expressed specifically in the milk. They could also be given human genetic diseases and used to test new treatments. This one is obviously more for monkeys than for sheep... Genetically altered animals might also produce organs that could be transplanted into humans with less chance of rejection than now exists. There is an active area to do this work with primates and pigs which could be used to grown relatively antigen free organs for transplant.

How did they come up with the name?
Dolly was cloned from the udder cell of a 6-year-old adult sheep. As you may have guessed, Dolly was named after Dolly Parton, the curvaceous country-and-Western singer.

The Family Line
Dolly did produce offspring, so if there was a genetic component to her early death the progeny will be studied to see if the detrimental effects are passed on. She first gave birth to Bonnie in April 1998 and then to three more lambs (which they didn't name) in 1999. In January of 2002 her condition caused concern when she was diagnosed with a form of arthritis.

The Telomeres of Dolly were shorter
Dolly yielded new information about the cloning process and how it can affect the clone and could add data to the idea that telomere length is connected to growing older. The researchers reported that Dolly's telomeres were 20 percent shorter than those of sheep who are not clones. The cells were taken from a six year old sheep and Dolly lived six years. 6+6=12 (the normal life span of a sheep). Is this a coincidence? Probably to early to tell at this point but the health problems Dolly had at this young age (arthritis and progressive lung disease) would be extremely rare in a middle-aged sheep. Dolly's offspring have been reported to have normal length telomeres.

A Timeline of Cloning...

1952 - The first clone to be created is from a tadpole. Robert Briggs and Thomas King used cells from a tadpole embryo to create identical tadpoles.

1976 - Transgenic mice are produced by Rudolf Jaenisch of the Salk Institute. The process involves the injection of human DNA into newly fertilized mouse eggs to produce mice that carry human genes. The offspring of the mice also contain these human genes. Different human diseases can be studied by creating mice with the appropriate genetic composition.

1978 - The world's first test-tube baby is conceived through in-vitro fertilization. Using the husband’s sperm, British doctors fertilize an egg in a petri dish and then implant the embryo in the uterus of the healthy woman (so she will be 25 years old this year...)

1987 - Sheep and cows are cloned from embryonic cells.

1997 - Dolly the sheep, the world’s first mammal cloned from a cell of an adult animal, was born in 1996, but her existence isn’t revealed to the world until February 24, 1997. Polly, the first sheep to contain a human gene was born during the same year.

1998 - An explosion in cloning based research occured when scientists at the University of Hawaii cloned more than 50 mice, several independent teams produced cloned cows. Some of these techniques reached the level or 80% efficiency. The original efficiency of Dolly's cloning batch was 1 in 300.

2000 - Oregon researchers reveal the existence of Tetra the cloned monkey. The company that produced Dolly announced a litter of five cloned pigs. The aim of this research effort is to produce pigs that can serve as a source of organ transplants for humans.

2001 - U.S. fertility specialist Panayiotis Zavos and a team of international scientists announced that couples had volunteered for an experiment to create cloned children. The team said it was poised to help infertile couples bear clones as early as 2003.

2002 - Texas A&M researchers announced that they had cloned a domestic cat. The calico-and-white female was dubbed "cc," for "CopyCat". The advance marks another step toward the routine cloning of household pets. Researchers call the company founded around the technology Genetic Savings and Clone. And I always thought they would call the company RePet like in that Arnold Schwarzenegger movie (The 6th Day).


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