User:Michaela Fredrickson/Pet cloning

Pet cloning
Pet cloning is one example of commercial animal cloning, and it is the process of using genes from one domestic (pet) animal to form a second, genetically identical, animal. This cloning is usually done through a process known as somatic cell nuclear transfer (SCNT). In this process, an oocyte is taken from a surrogate mother and put through enucleation, a process that removes the nucleus from inside the oocyte. Somatic cells are then taken from the animal that is being cloned, transferred into the blank oocyte in order to provide genetic material, and fused with the oocyte using an electrical current. The oocyte is then activated and re-inserted into the surrogate mother. The end result is the formation of an animal that is almost genetically identical to the animal the somatic cells were taken from. While SCNT was previously believed to only work using genetic material from somatic cells that were unfrozen or were frozen with cryoprotectant (to avoid cell damage caused by freezing), successful dog cloning in various breeds has now been shown using somatic cells from unprotected specimens that had been frozen for up to four days. Another method of pet cloning includes embryo splitting, the process of taking the blastomeres from a very early animal embryo and separating them before they become differentiated in order to create two or more separate organisms. When using embryo splitting, pet cloning must occur before the birth of the pet, and clones grow up at the same time that the original pet does (in a similar fashion to monozygotic twins).

Animal welfare
The mortality rate for cloned animals is higher than for those born of natural processes. This includes a discrepancy pre-birth, during birth, and after birth in survival rates and quality of life, leading to ethical concerns. Many of these discrepancies are thought to come from maternal mRNA already present in the oocyte prior to the transfer of genetic material as well as from DNA methylation, both of which contribute to the development of the animal in the womb of the surrogate. Some common issues seen with cloned animals are shortened telomeres, the repetitive end sequences of DNA whose decreasing length over the lifespan of an organism have been associated with aging ; large offspring syndrome, the abnormal size of cloned individuals due to epigenetic (gene expression) changes; and methylation patterns of genetic material that are so abnormal compared to standard embryos of the species being cloned as to be incompatible with life.

Pet cloning
While pet cloning is sometimes advertised as a prospective method for re-gaining a deceased companionship animal, pet cloning does not result in animals that are exactly like the previous pet (in looks or personality). Although the animal in question is cloned, there are still phenotypical differences that may affect its appearance or health. This issue was brought to light in the cloning of a cat named Rainbow. Rainbow's clone, later named CC, was genetically identical to Rainbow, yet CC's coloring patterns were not the same due to the development of the kitten inside the womb as well as random genetic disparities in the clone such as variable X-chromosome inactivation.

Despite its controversies, the study of pet cloning holds the potential to contribute to scientific, veterinary, and medical knowledge, and it is a potential resource in efforts to preserve endangered cousins of the cat and dog.

In 2005, California Assembly Member Lloyd Levine introduced a bill to ban the sale or transfer of pet clones in California. That bill was voted down.