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DNA cloning is a reproductive process that uses the genetic material of a single organism to create an offspring. It occurs naturally in some species that are capable of asexual reproduction, and scientists have cloned some animals using DNA cloning. The advantages of cloning include being able to carry on strong genetic traits and being able to produce new life without requiring a male and a female of the species. The disadvantages include the high expense, the possibility of genetic weaknesses being preserved and the fact that artificial clones have been found to have a shorter life span than others of the same species.
Few members of the animal kingdom are capable of asexual reproduction, though many bacteria, insects, fungi and plants reproduce in this manner. There are many advantages to DNA cloning, so scientists have made attempts to facilitate artificial cloning. A variety of animals have been successfully cloned, including sheep, cows, mice, goats, dogs, pigs and cats.
Asexual reproduction is advantageous for many reasons. Organisms that are capable of this can reproduce without expending energy in courtship and mating rituals. When separated from others of their kind, these organisms can still reproduce, ensuring the continuation of the species. Offspring is produced at a high rate, leading to large quantities of new organisms, and clones retain the exact same traits as their parents, which means that there are more individuals available to carry on a strong genetic line — the assumption being that the parent had to possess desirable traits to gain the opportunity to reproduce. Individual genetic strains, families and the species as a whole benefit from this reproductive strategy.
DNA cloning as a reproductive strategy does have disadvantages, however. Offspring of asexual reproduction are identical to the parent in every way. Any genetic weaknesses would be preserved. There is only one parent, so new genetic information is never introduced. This prevents the introduction of fresh traits and limits the growth potential of the colony.
Cell aging can also be a problem for asexual reproducers, because the natural degeneration of cells results in corrupted source material. For example, if a 50-year-old fungus formed a colony, the cellular age of the offspring also would be 50. This inability to reset the cellular age can affect the rate of reproduction, health and mortality of the colony.
The pros and cons of artificial cloning are theoretically the same as those of natural cloning. Clones made in a lab would have all of the strong traits of their parent. They would lack undesirable characteristics that normally would have come from a second parent.
Scientists could use various criteria to select the best candidates for cloning, which offers control over populations of animals used for food and recreation. For example, a cow that produces high-quality beef could be cloned ensuring a large supply of superior meat. Research facilities would be able to produce identical subjects for use in research and medical testing; the lack of variation between individuals would increase the validity of data. Tissue and individual organs could be cloned for use in surgeries, eliminating the need for organ donors and decreasing the risk of transplant rejection.
Limitations in current technology means that gene cloning is an imperfect science. These positive outcomes cannot be assured — in fact, they are highly unlikely. Research has shown that artificial clones do not survive as long as their parents, and fewer than 10 percent survive to adulthood.
More problematic, the causes of death of these clones are unknown. This high mortality rate suggests a flaw in the current cloning process. Deformities and fatal mutations are highly likely. This is a glaring disadvantage for those who wish to progress to human DNA cloning.
DNA cloning also presents many religious and ethical dilemmas. Concern has been raised over the legal status and rights of clones and the rights of parents. There also is concern over the social stigma of being a clone and the effect of cloning on interpersonal relationships.
@pleonasm - I don't think that's a reason to not bring them back. It would be tragic if someone brought back dodos and they did all die from a disease, but it's already tragic that they are gone forever. I think the reward of being able to bring them back would be worth the possibility of failure.
Unfortunately, that's not the main obstacle in cloning extinct animals. With existing animals, like cows, there are a lot of other cows that can carry a cloned embryo to term. But I don't think there is likely to be another bird that could properly form the egg of a dodo because they don't have any existing relatives that close.
And even with modern techniques DNA cloning vectors seem to be very hit or miss. Apparently they make thousands of attempts for every few that actually live to grow up.
@umbra21 - Cloning cons like that can also be seen in species where the natural gene pool is very small, like ones that have been brought back from the brink of extinction, or ones that have experienced an evolutionary bottleneck in the recent past.
This is one reason that some scientists have warned against trying to bring back extinct creatures like the dodo, because we usually have so few examples of DNA from them, it would leave any resulting animals completely vulnerable to disease or other genetic defects.
Human kind has actually already experienced a serious drawback in using DNA cloning as the sole means of reproduction in a species. Bananas in the wild are actually not a great food as they have a lot of large seeds, and the kind we eat are almost all grown from clones of a single hybrid variety.
But it isn't the same variety they used decades ago. That one was completely decimated by a disease so that the entire commercial banana population was lost within a very short period, because they were all essentially the same tree and that tree had no defense against this particular disease.
It's actually kind of weird to know that bananas we eat today don't taste the same as the ones our grandparents ate. And obviously we did overcome that problem by finding another type of banana to clone, but since it is also a clone the same thing could happen at any time.