? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ?
?{{B}}Clone Farm{{/B}}
? ?Factory farming could soon enter a new
era of mass production. Companies in the US are developing the technology needed
to "clone" chickens on a massive scale. Once a chicken with desirable traits has
been bred or genetically engineered, tens of thousands of eggs, which will hatch
into identical copies, could roll off the production lines every hour. Billions
of clones could be produced each year to supply chicken farms with birds that
all grow at the same rate, have the same amount of meat and taste the
same.
? ?This, at least, is the vision of the US’s National
Institute of Science and Technology, which has given Origen Therapeutics of
Burlingame, California, and Embrex of North Carolina $4.7 million to help fund
research. The prospect has alarmed animal welfare groups, who fear it could
increase the suffering of farm birds.
? ?That’s unlikely to put off
the poultry industry, however, which wants disease-resistant birds that grow
faster on less food. "Producers would like the same meat quantity but to use
reduced inputs to get there," says Mike Fitzgerald of Origen. To meet this
demand, Origen aims to "create an animal that is effectively a clone", he says.
Normal cloning doesn’t work in birds because eggs can’t be removed and
implanted. Instead, the company is trying to bulk-grow embryonic stem cells
taken from fertilized eggs as soon as they’re laid, "The trick is to culture the
cells without them starting to distinguish, so they remain pluripotent," says
Fitzgerald.
? ?Using a long-established technique, these donor
cells will then be injected into the embryo of a freshly laid, fertilized
recipient egg, forming a chick that is. a "chimera". Strictly speaking a chimera
isn’t a clone, because it contains cells from both donor and recipient. But
Fitzgerald says it will be enough if, say, 95 percent of a chicken’s body
develops from donor cells. "In the poultry world, it doesn’t matter if it’s not
100 percent," he says.
? ?Another challenge for Origen is to scale
up production. To do this, it has teamed up with Embrex, which produces machines
that can inject vaccines into up to 50,000 eggs an hour. Embrex is now trying to
modify the machines to locate the embryo and inject the cells into precisely the
right spot without killing it.
? ?In future, Origen imagines
freezing stem cells from different strains of chicken. If orders come in for a
particular strain, millions of eggs could be produced in months or even weeks.
At present, maintaining all the varieties the market might call for is too
expensive for breeders, and it takes years to breed enough chickens to produce
the billions of eggs that farmers need. |
单选集
