From the egg ,the nucleus was removed.The nucleus extracted from the mammary cell of the Finn–Dorsett ewe.This nucleus was fused with the enucleated egg of Scottish blackface ewe and further cell division was stimulated by electric current.After a few cell divisions,the embryo was implanted in another Scottish blackface ewe which later on gave birth to Dolly,the coloned sheep.

Introduction:
Dolly the sheep, the first cloned animal, was created by a team of scientists led by Dr. Ian Wilmut at the Roslin Institute in Scotland. The process of cloning involves transferring the nucleus of a somatic cell (body cell) into an egg cell whose nucleus has been removed. In the case of Dolly, the nucleus was taken from the mammary gland cell of a Scottish Blackface ewe.

Reasons for removing the nucleus:

1. Erase genetic information: The nucleus of the egg cell contains the genetic information of the donor animal. By removing the nucleus, the scientists were essentially erasing the genetic information of the egg donor and preparing it to receive the new nucleus from the somatic cell.

2. Eradicate epigenetic marks: Epigenetic marks are chemical modifications on the DNA that can influence gene expression. These marks play a crucial role in the development and differentiation of cells. By removing the nucleus, the scientists were also eliminating the epigenetic marks present in the egg cell. This allowed the newly introduced nucleus to have a fresh start without any epigenetic influences from the egg cell.

3. Reset developmental clock: The nucleus of an adult somatic cell contains the complete set of genetic information required for the development of an organism. However, it also carries the epigenetic marks and modifications acquired during the lifetime of the donor animal. By replacing the nucleus of the egg cell with the nucleus from a somatic cell, the scientists reset the developmental clock. The newly formed embryo would then develop based on the genetic instructions present in the somatic cell nucleus, as if it were a newly fertilized egg.

4. Ensure compatibility: The nucleus from the somatic cell of a Scottish Blackface ewe was chosen to ensure compatibility with the egg cell from a different sheep breed. This compatibility was essential for the successful development and growth of the cloned embryo. Using the nucleus from the same breed as the egg cell could have led to genetic incompatibilities and hindered the cloning process.

Conclusion:
The removal of the nucleus from the egg of a Scottish Blackface ewe in the process of cloning Dolly the sheep was necessary to eliminate the genetic information, epigenetic marks, and developmental influences of the egg donor. By replacing the nucleus with the nucleus from a somatic cell, the scientists ensured a fresh start and compatibility for the cloned embryo's development. This groundbreaking achievement in cloning paved the way for further advancements and research in the field of reproductive biology.