Remembering Dolly: Cloning Technology

Variations on a Theme: Different techniques used for cloning of animals are more alike than different.  However, they have become more efficient and more frequent since Dolly.  Did you know that Dolly was not the first animal cloned?  That honor went to cousins Megan and Morag

Dolly was not the first cloned mammal.  That honor went to two cousins of Dolly – Morag and Megan.  Researchers at the Roslin Institute announced the birth of Megan and Morag in May 1996.  Cloning twins, which started with an embryo of nine days old, who had a hundred cells.  The first cells of the embryo has a property called totipotency, the ability to isolate any cell type, but these cells are still identical to their parents before they have differentiated.  The research team led by Ian Wilmut, the totipotent cell divided embryos in culture dishes, thousands of cells in less than a week.

At the same time, hormone injections attention to the sheep, they produce many unfertilized eggs (secondary oocytes).  Researchers collected eggs surgically and in the laboratory, oocytes enucleated (removed cell nuclei).

The totipotent cell nuclear transfer into enucleated eggs in the culture was made by a process known as electro fusion, which involves using a small electrical pulse to melt all the cells in culture.  The fused cells were split into a new embryo, following the genetic instructions of the totipotent cell line.

Two hundred and fifty embryos implanted in surrogate mothers face painted black sheep in Scotland.  Of these, five survived the birth, three died within ten days, and only survived Morag and Megan last six months.

Megan and Morag were cloned from embryonic tissue, but Daisy was the first cloned adult mammal.  Dolly’s birth was announced in February 1997, also at the Roslin Institute.

With Dolly, the researchers started with adult sheep mammary (chest) cells.  They are different from embryonic cells are already specialized.  Differentiation occurs for cell genes in a cell not a cell is through a specialized process called DNA methylation.  To remove methylation, soaked the Roslin team adult mammary gland cells in the chemical bath which made them “forget” that he was specialized cells.  Essentially, cells were starved for five days.  Meanwhile, the core has entered a “resting” stage, delaying the division of genetic material in every heart.  Shortly afterwards, the cores were transferred to unfertilized eggs in electro fusion, and these developed into embryos.

Of the 277 trials, was one of the embryos Dolly.

In 1998, researchers at the Oregon Regional Primate cloned rhesus monkeys using electro fusion technique that produced Dolly the same, but the cells of many embryos have been used, such as rhesus monkeys, there were more who are twins.  In particular, experience has shown that transfer of nuclear technology and to reproduce the results of Roslin.  Animals such as primates, are more like clones of people today.

At the University of Wisconsin, a team led by Tanja Dominka embryos cloned from skin cells of an adult cow (News & Used Biotechnology Information 1998).  Taken from the cow’s ear, the skin cells into enucleated eggs entirely inserted in cattle.  An electrical impulse was used to fuse the two cells and make them start dividing into an embryo.  These embryos were implanted in the mother after breeding.

In 1997 a company called ABSGlobal said the birth of Gene, a calf Holstein came from a fetus of 30 days old (Infigen, Inc.).  In its proprietary process, a cell removed from the embryo removed and right to form a blastocyst the cells of sixteen sixties, thirty to two or four.  So each of these cells is to form a separate embryo.

Already in 1992 a company called Granada Biosciences has been active in animal cloning of embryonic tissue.  His method is to separate the individual cells from an embryo calf development.  Each cell is injected into an enucleated egg and implanted in the uterus of a surrogate mother cow.  Who has seen one hundred and twenty Success Rate.