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What I've learned
If you have an identical twin, the two of you are clones of each other.
That's not how we usually think of twins, as clones. But a clone is — and people tend to misunderstand this — a living thing whose genetic material is a copy of another.
You, yourself, can clone things without access to a fancy laboratory. Plants grown from cuttings are clones. So the apples you've eaten all your life (I'm partial to Granny Smiths.) are, in reality, clones. So are most bananas, potatoes, grapes, pears, and peaches. We don't call the process of producing such foods "cloning," we call it "vegetative propagation."
If a cow had twins, would one of them be less safe to eat? No. The fact that each was a genetic copy of the other would not matter at meal time.
Scientists are now doing in the laboratory, what Mother Nature occasionally does in the womb. The Federal Food and Drug Administration [FDA] has published a "Primer on Cloning and Its Use in Livestock Operations" that says:
"Some people incorrectly believe that clones spring forth fully formed, or are grown in test tubes. This is just not the case.
Clones are born just like other animals. They are similar to identical twins, only born at different times. Just as twins share the same DNA, clones have the same genes as the donor animal. A clone is not a mutant, nor is it a weaker version of the original animal."
Cloning should not be confused with genetic engineering, which is a whole other can of worms. The FDA says, "Cloning is not the same as genetic engineering. Genetic engineering involves adding, taking away, or modifying genes, while cloning does not change the gene sequence."
You may be saying, "Be all that as it may, I want my cows and horses and sheep to be produced the old-fashioned way, with a male and a female rutting in the barnyard."
Uh, when's the last time you spent any time in a barnyard? Most dairy farmers don't even own a bull these days.
The FDA points out that:
". . . many farmers use assisted reproductive technologies for breeding. These include artificial insemination, embryo transfer, and in vitro fertilization (a process by which egg and sperm are united outside the body). Artificial insemination was first documented in the breeding of horses in the 14th century. The first successful embryo transfer of a cow was in 1951, and the first in vitro fertilization-derived animal was a rabbit born in 1959.
"Livestock production in the United States now uses all these methods regularly. For example, most dairy farms don’t have bulls, so more than 70 percent of the Holstein cows bred in the United States are artificially inseminated. The frozen semen can come from a bull many miles, or even many states, away."
Though you can clone fruits and vegetables in your yard, cloning animals requires a fancy lab. Most cloning today involves taking an immature egg from a female animal (often from ovaries obtained at the slaughterhouse), and removing the nucleus, which contains the genes. Scientists then replace the nucleus with one from a cell of a donor animal. If all goes well, the donor nucleus fuses with the egg, starts dividing, and an embryo begins to form.
The embryo is implanted in the uterus of a surrogate female. The baby grows and is delivered just like any other baby animal.
One of the interesting aspects of cloning is that clones don't necessarily look identical, either to the donor or to each other. They have the same genes, but those genes can be expressed differently in each clone. This different expression of the same genes can often be observed in human identical twins. I've seen identical twins that are almost impossible to tell apart, and I've seen identical twins that look more like fraternal twins. Same genes, different freckles, different hair texture and color, different shape to the face or eyes or nose. Same genes expressed differently. Huh.
For now, cloning of animals is use primarily for breeding purposes, not for direct food production. However, the FDA, in risk assessments, said it "could not distinguish a healthy clone from a healthy conventionally bred animal. All of the blood values, overall health records, and behaviors were in the same range for clones and conventional animals of the same breed raised on the same farms. FDA also observed that milk from dairy clones does not differ significantly in composition from milk from conventionally bred animals."
I don't know that I'm in favor of the cloning of animals, but I am less freaked out about it than about genetic engineering, which is a path too dangerous to travel down, despite its touted benefits.