In 1996, one of the most famous cloning cases occurred when Dolly was made udder cell of a 6-year-old sheep. But what exactly is cloning? it’s roughly defined as “the creation of an exact genetic replica of a small segment of DNA, of a cell or of an entire organism”. However, the resulting creature is not always a carbon copy of its source. The genetic result depends on the specific method employed. Scientists perform three different types of cloning:
In a method perhaps less exciting than that which led to Dolly’s conception, genetic or molecular cloning creates copies of genes or segments of DNA. It is often used to study particular genes in the laboratory.
In this case, scientists to take a specific segment of DNA and place it in self-replicating genetic material called plasmid DNA inside a bacterial cell. They then put the resulting recombinant DNA (combined human and bacterial) into a host. Examples of hosts include bacteria, yeasts, and mammalian cells. This method ensures that scientists can work with multiple copies of the specific gene of interest.
Gene cloning has authorized laboratories to develop vaccines and antigen tests, among other breakthroughs. Scientists can also identify a useful trait and use it in the genetic modification of seeds, such as the natural pest resistance gene of a particular plant.
This technique creates a genetic copy of an animal. Besides Dolly, scientists have so far cloned a cat, a horse, a deer, a rabbit, an ox and a monkey, to name a few.
It is usually accomplished by somatic cell nuclear transfer (SCNT). Before SCNT has progressed considerably in the 1980s and 1990s, cloning was usually done by division of embryos. This method starts with share an early-stage multicellular embryo to make two âhalf-embryosâ. These are implanted in the uterus of a surrogate mother who does not share genetic material with the original embryos. This mirrors how monozygotic twins naturally form in the womb.
In the SCNT approach, researchers use an electric current to fuse an adult somatic cell (non-reproductive or sperm) with an egg whose nucleus has been removed, triggering fertilization and cell division. The transformed egg is then placed in a test tube, where it develops into an embryo. Finally, this embryo is implanted in the uterus of a female animal.
Reproductive cloning does not always lead to exact duplicate: for example, Dolly, which was created via SCNT, was constructed from an egg donated by a black-faced sheep and chromosomal DNA from the mammary gland of a white-faced sheep (which is Why she was named after Dolly Parton). So you can’t necessarily call her a real white-faced sheep, because she has a little bit of black-faced sheep in her – in the form of mitochondrial DNA, which doesn’t live in the nucleus.
Overall, animal cloning has been recognized as ineffective because the resulting embryos usually cannot lead healthy lives. Of 277 sheep embryos cloned as part of the experiment at the Roslin Institute at the University of Edinburgh, Dolly was the only one born alive. And as they grow, clones can exhibit organ defects, premature aging, and immune system issues. Dolly only reached about half the average lifespan of a normal sheep because, due to the cloning process, she received mature chromosomes from an adult organism which are shorter than those from a typical embryo. This speeds up cell death in an animal and limits its lifespan.
Stem cells, which are non-specialist and can be renewed by cell division, are from a cloned embryo. When they are differentiated or transformed into specific cell types, they can be used to test new drugs. The labs are also aiming to transplant patients with tissue generated from their own cloned cells to avoid rejection. For example, a person with type 1 diabetes might benefit to from replacement pancreatic cells that produce insulin.
The surprising benefits of animal copying
Reproductive cloning can also contribute to important medical advances. As for drug testing, it could To allow researchers to work with several animals having exactly the same genetic makeup. Laboratories could also to create copies of genetically engineered animals that make milk with a protein that helps blood clot in humans. In 2009, the FDA approved the drug ATryn, which was manufactured possible by cloning goats, for the prevention of thrombosis.
Cloning could also help bring species back from extinction. Last February, scientists announced that they had with success cloned the first endangered species native to North America, a black-footed polecat. They worked with the frozen remains of a preserved ferret in 1988, when DNA technology was in its infancy. Cloning could even save completely extinct species, but it requires live cell samples that are not generally available to long-extinct animals like mammoths. This is why supporters of the de-extinction of mammoths are rather search in genetic engineering (via a woolly mammoth-Asian elephant hybrid).
Can we clone humans?
Besides the ethical objections concerning the copy Homo sapiens, the process also presents a logistical challenge. We primates have spindle-shaped proteins, crucial for cell division, located near the chromosomes of our unfertilized eggs. When the nucleus is deleted from the egg during the cloning process, spindle proteins are also extracted. This disrupts the growth of the cloned organism. In addition, ultraviolet light and certain dyes involved in removing the nucleus of the egg could to prevent the primate cell to grow. While some groups have claimed to have successfully multiplied humans, the spindle protein problem makes the results of their experiments questionable.