In 1972, Oliver Ryder, geneticist at San Diego Zoo decided to collect as much animal skin samples as possible, hoping that tissue bank might be useful in future attempts to save endangered animals. He didn’t know that animals will be created using somatic cells in the future. Stored tissues were named “Frozen Zoo” thanks to preservation method used (liquid nitrogen). Until now, this collection grew to impressive number of ~9 000 samples belonging to ~1 000 different vertebrate species. Although initial idea wasn’t to create a gene pool that will be used for animal cloning, latest techniques and high rate of extinction made “Frozen Zoo” serving that purpose exactly.
First attempts to clone threatened animal species started at the beginning of the 2001 using South Asian ox – guar. SCNT (stem cell nuclear transfer) using guar’s somatic cells and cow’s egg resulted in successful embryo development, that was seeded into cow’s uterus. Noah was born seemingly healthy, but 2 days later – he died due to infection.
In 2000, Spanish ibex, known as bucardo, went extinct. That was the first time that scientist tried to clone extinct animal. Nucleus derived from ibex’s skin cell was implanted into de-nucleated egg of domestic goat - its closest relative. New ibex was born, but died soon after the birth due to severe lung defect. As with Dolly the sheep, a lot of attempts were made before viable embryo that could survive until the birth was created. In the case of bucardo, 439 SCNT were made, 57 embryos were implanted, 7 embryos resulted in pregnancy and just one managed to survive until the birth. He lived for 7 minutes: inability to breath normally prevent him to live longer.
Success rate of cloning is 1%. Beside the low success rate, born animals are unhealthy and prone to various infections that doesn’t keep them alive for a long period.
In 2007, Japanese scientist concluded experiments on mice, revealing that adult somatic cells could be reverted to embryo like stem cells. Those cells were named “induced pluripotent stem cells” (iPS cells) and they could be used for creating any cell lineage you want. Oliver Ryder and his co-workers from San Diego Zoo are using iPS cells to create Northern white rhino, snow leopard and small West African monkey replicas as the number of those species is incredibly low (7 remaining individuals of white rhino are kept in captivity).
Besides “saving” animals that are still alive, or that are extinct few years ago, scientific appetites are growing bigger. How about creating Woolly Mammoth using DNA from his leftovers found under Siberian permafrost recently? Japanese and Russian scientist promise to create a mammoth in couple of years, using mammoth’s nucleus and elephant’s egg. Only problem with resurrecting mammoth is age of the DNA and damage found in his genetic material. However, using modern methods, 80% of mammoth genome is decoded. Creating chimera animal could solve the problem: stem cell derived from mammoth (using iPS method) placed near elephant embryo would affect early embryo development, resulting in animal having tissues created out of both mammoth and elephant cells. We are closer that we think to see mammoth (probably weak and unhealthy, but still successfully created) walking the Earth again.
What is making me really angry and sad is that mankind is responsible for all recently (couple of hundred years) noted extinctions. Why don't we use money and effort made in cloning animals to prevent extinction instead? Don’t you think that those kinds of experiments are cruel to the animals? Who ask female elephant if she is willing to be a surrogate mother to a mammoth? Would you like to be a surrogate mother to a chimpanzee, as its closest relative? I don’t think so. We managed to destroy so many beautiful things on the planet Earth, but driving animals extinct instead preserving them and then resurrecting them just to show future generation how mammoth looked like before he went extinct - I just don’t get it! If human ever become critically endangered – please don't clone me!