BBC Earth (Asia) - - Update -

A cell in an early em­bryo has some­thing akin to a su­per­power. It can trans­form into any part of the or­gan­ism, a skin cell per­haps, a muscle cell, a nerve cell or a blood cell. Be­fore Dolly, ev­ery­one as­sumed that in mam­mals this process of spe­cial­i­sa­tion, so-called ‘dif­fer­en­ti­a­tion’, was ir­re­versible.

Dolly proved other­wise.

Sci­en­tists start with an egg cell.

The nu­cleus (the part of the cell that con­tains the ma­jor­ity of the ge­netic ma­te­rial) is re­moved from the egg cell. A sin­gle dif­fer­en­ti­ated cell is picked up by a tiny nee­dle. In Dolly’s case, the dif­fer­en­ti­ated cell was an ud­der cell from an adult donor.

The cell is in­jected into the egg cell and a small elec­tri­cal pulse is used to fuse the nu­cleus into its new en­vi­ron­ment and to kick-start cell divi­sion.

The egg cell and dif­fer­en­ti­ated cell fuse. You can see in this im­age that the egg cell now has a nu­cleus (up­per cen­tre). The em­bryo is im­planted into the uterus of a sur­ro­gate fe­male. She car­ries the clone to term.

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