- "Test fertilization of an artificial ovum. My hand shook as I held the tiny eye dropper. One drop, two drops... there! The genie was out of the bottle."
- —John Hammond(src)
When the dinosaur nucleus, containing all chromosomes, is created the nucleus has to be injected into an unfertilised egg cell. Such cells are called Oocytes. This cell will multiply itself, forming an embryo. The embryo can only develop into a dinosaur if it is inserted into an egg. An egg cell has to be found or created that is able to read dinosaur DNA.
Suppose we would have an ideal egg cell, containing dinosaur mitochondria and everything else a dino cell needs. How would an InGen scientist get the dinosaur nucleus into this cell? In Jurassic Park: Trespasser John Hammond tells how he himself did it with an eye dropper. However, in nuclear transfer eye droppers are not used.
This technique is based on reproductive cloning, which was used to clone Dolly.
Some Jurassic Park critics have claimed that it is impossible to clone egg-laying animals. For example, Brian Switek told Mental Floss this:
Since birds have outsourced the growth of their offspring outside the body, there may not even be a way to successfully clone a bird, and so there would be no method by which we could bring dinosaurs back even if we had all the requisite raw materials. It’d be like assembling all the materials for a cake and turning on the oven, but having no clue about the cooking chemistry of how to achieve the desired, tasty result.
However, this is not true. Although no egg-laying animals have ever been cloned, it IS possible to remove the nucleus from a bird cell and place it in another egg. Liu and his team successfully performed nuclear transfer by removing the blastodermal cells of a chicken and placing them into rabbit occytes, although they didn't become viable offspring. This indicates that nuclear transfer of egg-laying animals is possible.
Chicken eggs have also been fertilized in-vitro. Tanaka et al managed to produce viable chicks by removing egg cells from hens and fertilizing them with sperm. The cells were then inserted into the chicken oviduct. The hens laid 76 eggs, 53 of which had calcified egg shells, and 31 were fertile.
The type of egg cell into which the dinosaur DNA is translocted is very important. The first stages of embryonic development are regulated by transcription factors in the donor cell.
If the same method that created the Chickenosaurus is performed on an ostrich, the resulting creature (Ostrichosaurus ?) is the best candidate to be used to breed small theropod dinosaurs.
Cloning is already difficult when the DNA and egg cell of the same species are used. Research on interspecies cloning has only been done for mammals. When the DNA and donor cell are from the same genus, it can lead to living offspring. When the nucleus of a Yak (both belong to the genus Bos) was inserted into a Cow egg, the embryo successfully grew into a Yak.
However, when the DNA and egg cell belong to a different genus, Family, Order or Class, cloning is unsuccessful. In most cases the fertilised egg is able to grow into a Blastocyst (early form of embryo), but the implantation of the cells to the wall of the uterus fails. Embryos made from a rabbit egg and cat DNA were able to adhere to the uterus wall, but failed produce living offspring. This is most likely because the donor egg fails to correctly activate the genome.
Since all non-avian dinosaurs are extinct, it will be a challenge to find a compatible egg cell. Even the Ostrich and the very Ostrich-looking Struthiomimus (meaning "Ostrich mimic") belong to different Orders. The ostrich belongs to the Palaeognathae Order, while the Struthiomimus belongs to Ornithomimosauria. Many Jurassic Park critics have noted this problem. For example, Ryan Whitwam of Extremetech.com wrote:
Modern cloning techniques involve replacing the nucleus and genetic material in an egg cell with the nucleus of the animal you are trying to clone. The problem being, we don’t have a dinosaur to donate that egg. We also lack an intact dino nucleus to take up residence in a cell. You can’t grow a dinosaur with just a pile of DNA. Scientists would need a very similar animal to even consider cloning a dinosaur, and after 65 million years, that’s not likely.
However, when Human DNA was inserted into Rabbit egg cells, the resulting cells showed correct gene expressing and cell differentiation. For ethical reasons, it wasn't checked whether these cells could grow into living offspring. However, these results show that even if the DNA and egg belong to different orders, the egg is able to correctly activate the genome's genes.
Therefore, it is possible that Ostrichosaurus eggs could be used to clone small theropods. If Struthiomimus or Velociraptors are successfully cloned, their egg cells could be used to clone larger theropods like Dilophosaurus or T. rex. If Jurassic theropods like Allosaurus or Dilophosaurus are cloned, their egg cells might be useful to clone more primitive theropods like Herrerasaurus.
Maybe Herrerasaurus eggs could be used to clone sauropods. It remains to be seen if egg cells can be produced to clone Ornithischian d chimera's development, the resulting organism would be an ostrich or emu that has the reproductive organs of a Struthiomimus.
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