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Is it necessary to insert the nucleus of somatic cell of any animal in an egg cell of the same type of animal in cloning? Can we insert sheep somatic cell in cow egg cell and have a successful cloning? If so,why is it possible? If not,why is not it possible?
Question Date: 2012-10-16
Answer 1:

To answer your question, it does not appear to be possible to insert the somatic nucleus of an animal into the egg of an animal of a different species and generate a live clone. The reason for this is that development of an embryo is an incredibly sensitive process even in regards to naturally occurring fertilization. When an embryo initially begins to divide, many proteins present in the egg are responsible for ensuring that cell division occurs properly and that those cells begin to express the correct genes at the correct times.

When development begins, cells must differentiate from being a general cell type, to a specific tissue that only expresses a small number of the genes present in the nucleus. This happens early, and is stimulated by signals already present inside the original egg. For this to work, the proteins present in the egg must recognize specific sequences found in the DNA of the nucleus. In the case of cloning, the DNA being inserted into the egg must come from the same species, or the proteins inside the egg won’t recognize the sequences they are supposed to interact with. Imagine that the DNA of each animal is a set of instructions for the creation of that animal, and each is written in a unique language that only animals of that species can understand. For example, if you were a protein in the egg and the only language you knew was English, it would be pretty hard to put together an animal whose instructions were written in Japanese. Essentially, if you put the nucleus of one species into the egg of another species, the proteins in the egg won’t understand how to read the DNA instructions that tell it how to put the new animal together.

Also, there is a second set of DNA inside the egg called “mitochondrial DNA”. This DNA is always inherited directly from the mother and encodes another special set of genes that are involved in generating energy for the cell. This DNA must also match the species that the nucleus comes from or the cell will have difficulties creating energy, and without energy the cell can’t survive.

Even when using an egg from the same species, cloning is a very difficult process with a very low success rate because of all the problems that arise from using a differentiated nucleus to create all the tissue types in the body.

When scientists cloned Dolly the sheep click here in dolly they had to generate 98 embryos to get 16 that were able to divide into a multicellular embryo, of these only 8 developed into fetuses and only 1 (Dolly) survived more than a few days after being born. So you can see that even when using the same species for the egg and nuclear DNA, cloning is still an imperfect process that requires many attempts to actually work. Hope that helped!

Answer 2:

Good question - it almost certainly depends on the animal. More closely related animals will be more able to bear the offspring of another animal than distantly-related animals. You need the nucleus of another cell, though, because otherwise your new cell won't have DNA.

This clothing method is also fraught with problems. First, the DNA in a somatic cell will have lost some of its telomeres, strings of adenozines added to the ends of the chromosomes and which are partially consumed each time a cell divides (note: sex cells regenerate their telomeres). This limits the number of times a cell can divide, and is one of the reasons for aging. Your clone would grow old sooner than the original animal would.

Additionally, the chemistry of the mother cell also affects the expression of the DNA, so the animal won't be a perfect clone for this reason, either.

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