Dolly-The Cloned Sheep

Dolly-The Cloned Sheep

1. Dolly-The Cloned
Sheep
Introduction:
Dolly was a female Finn Dorset sheep, and
the first mammal cloned from an
adult somatic cell. It was born on July 5th,
1996, at the Roslin Institute in Edinburgh,
Scotland. The name "Dolly" came from a
suggestion by the stockmen who helped with her birth, in honor of Dolly Parton,
because it was a mammary cell that was cloned. Her birth was announced on
February 22, 1997. The sheep was originally code-named "6LL3".
Process of Dolly Production:
Dolly was born on 5 July 1996 and had three mothers: one provided the egg, another
DNA, and a third carried the cloned embryo to term.

She was created using the
technique of somatic cell nuclear transfer.
Somatic cell nuclear transfer (SCNT):
 The nucleus of a somatic (body) cell is transferred to the cytoplasm of an
enucleated egg (an egg that has had its own nucleus removed).
 Once inside the egg, the somatic nucleus is reprogrammed by egg
cytoplasmic factors to become a zygote (fertilized egg) nucleus.
 The hybrid cell is then stimulated to divide by an electric shock, and when it
develops into a blastocyst it is implanted in a surrogate mother.
 Dolly had three mothers. One mother gave Dolly her DNA, one mother
supplied an egg, and the third mother, her surrogate mother, gave birth to
her.

2. Steps involved in the production of Dolly:
1. Enucleate the eggs produced by Scottish Blackface ewes (female sheep).
 Treat the Scottish Blackface ewes with gonadotropin-releasing hormone
(GnRH)to cause them to produce oocytes ready to be fertilized(for
arrestingthe oocyte or egg at metaphase of the second meiotic division
(meiosis II).
 Plunge a micropipette into the egg over the polar body and suck out
not only the polar body but the haploid pronucleus within the egg.
2. Fuse each enucleated egg with a diploid cell growing in culture.
 Cells from the mammary gland of an adult Finn Dorset ewe are grown
in tissuculture.
 Donor cells and enucleated recipient cells are placed together in
culture.
3. The cultures are exposed to pulses of electricity to
 Cause their respective plasma membranes to fuse;

3.  Stimulate the resulting cell to begin mitosis (by
mimicking the stimulus of fertilization).
4. Culture the cells until they have grown into a morula (solid mass of cells) or
even into a blastocyst (6 days).
5. Transfer several of these into the uterus of Scottish Blackface ewes for
implantation.
6. The result: One ewe gave birth (148 days later) to Dolly.
Dolly’s probability
 Cells taken from a six-year-old Finnish Dorset ewe and cultured in a
lab.
 277 cells then fused with 277 unfertilized eggs (each with the nucleus
removed)
 29 viable reconstructed eggs survived and were implanted in surrogate
Blackface ewes.
 1 gave birth to Dolly.
Life of Dolly:
 Dolly lived her entire life at the Roslin Institute in Midlothian.
 There she was bred with a Welsh Mountain ram and produced six lambs in
total.
 Her first lamb, named Bonnie, was born in April 1998.
 The next year Dolly produced twin lambs Sally and Rosie, and she gave birth
to triplets Lucy, Darcy and Cotton in 2000.
 In late 2001, at the age of four, Dolly developed arthritis and began to walk
stiffly. This was treated with anti-inflammatory drugs.
Death:

4.  On 14 February 2003, Dolly was euthanised (act of putting an animal to
death) because she had a progressive lung disease and severe arthritis.
 A Finn Dorset such as Dolly has a life expectancy of around 11 to 12 years, but
Dolly lived 6.5 years.
 A post-mortem examination showed she had a form of lung cancer
called ovine pulmonary adenocarcinoma, which is a fairly common disease of
sheep and is caused by the retrovirus JSRV.