Timeline

Explore the history of livestock cloning.

Animal cloning has been around since the beginning of the 20th century, but livestock cloning was only developed in the last few decades. The journey from embryonic to somatic cells culminated into scientists' ability to clone many different kinds of animals, from sheep to monkeys to even humans in the future.

A History: From Embryonic Cells to Somatic Cells

1902

Artificial Embryo Twinning

Hans Spemann split two cells in a salamander embryo, and each developed into a separate salamander. This showed that relatively underdeveloped embryos can be split to form identical organisms.

1928

The Importance of Embryonic Nuclei

Hans Spemann then demonstrated that if a single cell with a nucleus was separated from an embryo, the cell would become a new salamander. His experiment, an early example of nuclear transfer, showed that an embryonic nucleus is essential to an organism's growth and can serve as the nucleus in an egg.

1952

The First Nuclear Transfer

Robert Briggs and Thomas King removed the nucleus from a frog egg and transplanted an embryonic nucleus there instead. This cell eventually became a tadpole. Their success furthered the idea of nuclear transfer. They also provided evidence that nuclei are essential to organisms' development, and that less developed embryonic cells are best for cloning.

1958

The First Somatic Cell Nuclear Transfer

John Gurdon moved the nucleus of a tadpole's somatic cell to a frog egg (whose nucleus was removed). The egg yielded genetically identical tadpole clones. This experiment was the first example of nuclear transfer with somatic, rather than embryonic, cells.

The First Nuclear Transfer: Mammals

Steen Willadsen fused a cell from a lamb embryo to an egg cell (whose nucleus was removed); the embryos were then placed in a surrogate mother. Eventually, 3 lambs were born. This showed that a mammal could be cloned through nuclear transfer of embryonic cells.

1984

Cow Cloned With Embryonic Cell

Neal First, Randal Prather, and WIllard Eyeston created 2 cloned cows, showing that cows could be cloned through nuclear transfer with embryonic cells.

1987

1996

Nuclear Transfer With Lab Cells

Ian Wilmut and Keith Campbell transferred cultured sheep cells' nuclei to egg cells with their nuclei removed. This shows that even cultured cells can be used to clone through nuclear transfer.

1996

Dolly the Sheep Created with SCNT

Ian Wilmut and Keith Campbell transferred a somatic cell (an adult udder cell) to an egg, creating Dolly the sheep after 276 tries. It was the first time a differentiated adult somatic cell, which can't activate certain genes like embryonic cells can, was used successfully. This sparked controversy over cloning.

1997

Nuclear Transfer with Genetically Engineered Lab Cells

Angelika Schnieke, Ian Wilmut, and Keith Campbell carried out nuclear transfer using sheep somatic cells (grown in a lab) that contained Factor IX, a gene that can help treat hemophilia. They created Polly, whose milk had Factor IX in it. This experiment illustrated the possible medical uses of animal cloning.

2001

Endangered Animals Are Cloned

Multiple scientists cloned the gaur and mouflon, two endangered animals, with SCNT to possibly save endangered species. Other scientists cloned the extinct bucardo, but the clone died soon after birth.

2007

Nuclear Transfer Creates Primate Embryonic Cell

Shoukhrat Mitalipov created an embryo from an adult monkey cell and an egg; this embryo's cells are called embryonic stem cells. Stem cells could possibly lead to "human therapeutic cloning" to treat disease.

Human Stem Cells Are Created

Shoukhrat Mitalipov fused a human skin cell with an egg cell to create a human embryo from which embryonic stem cells could come from.

2013

(B-1)

To explore more examples of cloned animals (not just livestock!), click here.