Clones are organisms that are exact genetic copies. Every single bit of their DNA is identical.
Clones can happen naturally-identical twins are just one of many examples. Or they can made in the lab.
Many people first heard of clonning when Dolly the sheep showed up on the scene in 1997. artificial cloningtechnologies have been around for much than dolly. though.
here two ways to make an exact genetic copy of an organism in a lab; artificial embryo twinning and somatic nuclear transfer.
1. Artificial Embryo Twinning
Artificial embryo twinning is a relatively low-tech way to make clones. As the name suggests, this technique mimics the natural process that creates identical twins.
In nature, twins form very early in development when the embryo splits in two. Twinning happens in the first days after egg and sperm join, while the embryo is continues dividing on its own, ultimately developing into separate, complete individuals. Since they developed from the same fertilized egg, the resulting individuals are genetically identical.
Artificial embryo twinning uses approach, but it is carried in a Petri dish instead of inside the mother. A very early embryo is saperated into individual cells, which are allowed to divide and develope for a short time in the Petri dish. The embryos are then placed into a surrogate mother, where they finish developing. Again, since all the embryos came from the same fertilized egg, they are genetically identical.
(Artificial Embryo Twinning)
2. Somatic Cell Nuclear Transfer
Somatic nuclear transfer also called nuclear transfer, uses a different approach than artificial embryo twinning, but the produces the same result : an exact genetic copy, or clone, of an individual. This was the method used to ceate Dolly the Sheep.
(SCNT = Somatic Cell Nuclear Transfer)
What does SCNT mean ? Let's take it apart
Somatic Cell : A somatic cell is any cell in the body other than sperm and egg, the two types of reproductive cells. Reproductive cells are also called germ cells. In mammals, every somatic cell has two complete sets of chromosomes, whereas the germ cells have only one complete set.
Nuclear : The nucleus is a compartment that holds cell's DNA. The DNA is divided into packages called shromosomes, and it contains all the information needed to form an organism. It's small differences in our DNA that make each of us unique.
Trasnfer : Moving an object from one place to another. To make Dolly sheep, researchers isolated a Somatic Cell from an adult female sheep. Next they removed the nucleus and all of its DNA from an egg cells. Then they transferred the nucleus from the somatic cell to the egg cell. After a couple of chemical tweaks, the egg cell, with its new nucleus, was behaving just like a freshly fertilized egg. It developed into an embryo, which was implanted into a surrogate mother an carried to term. ( The transfer step is most often done using an electrical current to fuse the membrantes of the egg and the somatic cell).
The lamb Dolly, was an exact genetic replica of the adult female sheep that donated the somatic cell. She was the first ever mammal to be cloned from an adult somatic cells.
(Cloning of Dolly Sheep)
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