WHAT IS CLONING AND COULD WE ONE DAY CLONE HUMANS?
What is cloning?
Cloning describes several different processes that can be used to produce genetically identical copies of a plant or animal.
In its most basic form, cloning works by taking an organism's DNA and copying it to another place.
There are three different types of artificial cloning: Gene cloning, reproductive cloning and therapeutic cloning.
Gene cloning creates copies of genes or parts of DNA. Reproductive cloning creates copies of whole animals.
Therapeutic cloning produces embryonic stem cells for tests aimed at creating tissues to replace injured or diseased tissues.
Dolly the Sheep was cloned in 1996 using a reproductive cloning process known as somatic cell nuclear transfer (SCNT).
This takes a somatic cell, such as a skin cell, and moves its DNA to an egg cell with its nucleus removed.
Another more recent method of cloning uses Induced pluripotent stem cells (iPSC).
iPSCs are skin or blood cells that have been reprogrammed back into an embryonic-like state.
This allows scientists to design them into any type of cell needed.
Could we ever clone a human?
Currently there is no scientific evidence that human embryos can be cloned.
In 1998, South Korean scientists claimed to have successfully cloned a human embryo, but said the experiment was interrupted when the clone was just a group of four cells.
In 2002, Clonaid, part of a religious group that believes humans were created by extraterrestrials, held a news conference to announce the birth of what it claimed to be the first cloned human, a girl named Eve.
This was widely dismissed as a publicity stunt.
In 2004, a group led by Woo-Suk Hwang of Seoul National University in South Korea published a paper in the journal Science in which it claimed to have created a cloned human embryo in a test tube.
In 2006 that paper was retracted.
According to the National Human Genome Research Institute, from a technical perspective cloning humans is extremley difficult.
'One reason is that two proteins essential to cell division, known as spindle proteins, are located very close to the chromosomes in primate eggs,' it writes.
'Consequently, removal of the egg's nucleus to make room for the donor nucleus also removes the spindle proteins, interfering with cell division.'
The group explains that in other mammals, such as cats, rabbits and mice, the two spindle proteins are spread throughout the egg.
HOW WAS DOLLY THE SHEEP CREATED?
Dolly was the only surviving lamb from 277 cloning attempts and was created from a mammary cell taken from a six-year-old Finn Dorset sheep.
She was created in 1996 at a laboratory in Edinburgh using a technique called somatic cell nuclear transfer (SCNT).
The pioneering technique involved transferring the nucleus of an adult cell into an unfertilised egg cell whose own nucleus had been removed.
An electric shock stimulated the hybrid cell to begin dividing and generate an embryo, which was then implanted into the womb of a surrogate mother.
Dolly was the first successfully produced clone from a cell taken from an adult mammal.
Dolly's creation showed that genes in the nucleus of a mature cell are still able to revert back to an embryonic totipotent state - meaning the cell can divide to produce all of the difference cells in an animal.
What is cloning?
Cloning describes several different processes that can be used to produce genetically identical copies of a plant or animal.
In its most basic form, cloning works by taking an organism's DNA and copying it to another place.
There are three different types of artificial cloning: Gene cloning, reproductive cloning and therapeutic cloning.
Gene cloning creates copies of genes or parts of DNA. Reproductive cloning creates copies of whole animals.
Therapeutic cloning produces embryonic stem cells for tests aimed at creating tissues to replace injured or diseased tissues.
Dolly the Sheep was cloned in 1996 using a reproductive cloning process known as somatic cell nuclear transfer (SCNT).
This takes a somatic cell, such as a skin cell, and moves its DNA to an egg cell with its nucleus removed.
Another more recent method of cloning uses Induced pluripotent stem cells (iPSC).
iPSCs are skin or blood cells that have been reprogrammed back into an embryonic-like state.
This allows scientists to design them into any type of cell needed.
Could we ever clone a human?
Currently there is no scientific evidence that human embryos can be cloned.
In 1998, South Korean scientists claimed to have successfully cloned a human embryo, but said the experiment was interrupted when the clone was just a group of four cells.
In 2002, Clonaid, part of a religious group that believes humans were created by extraterrestrials, held a news conference to announce the birth of what it claimed to be the first cloned human, a girl named Eve.
This was widely dismissed as a publicity stunt.
In 2004, a group led by Woo-Suk Hwang of Seoul National University in South Korea published a paper in the journal Science in which it claimed to have created a cloned human embryo in a test tube.
In 2006 that paper was retracted.
According to the National Human Genome Research Institute, from a technical perspective cloning humans is extremley difficult.
'One reason is that two proteins essential to cell division, known as spindle proteins, are located very close to the chromosomes in primate eggs,' it writes.
'Consequently, removal of the egg's nucleus to make room for the donor nucleus also removes the spindle proteins, interfering with cell division.'
The group explains that in other mammals, such as cats, rabbits and mice, the two spindle proteins are spread throughout the egg.
HOW WAS DOLLY THE SHEEP CREATED?
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| Dolly the sheep made history 20 years ago after being cloned at the Roslin Institute in Edinburgh. Pictured is Dolly in 2002 |
Dolly was the only surviving lamb from 277 cloning attempts and was created from a mammary cell taken from a six-year-old Finn Dorset sheep.
She was created in 1996 at a laboratory in Edinburgh using a technique called somatic cell nuclear transfer (SCNT).
The pioneering technique involved transferring the nucleus of an adult cell into an unfertilised egg cell whose own nucleus had been removed.
An electric shock stimulated the hybrid cell to begin dividing and generate an embryo, which was then implanted into the womb of a surrogate mother.
Dolly was the first successfully produced clone from a cell taken from an adult mammal.
Dolly's creation showed that genes in the nucleus of a mature cell are still able to revert back to an embryonic totipotent state - meaning the cell can divide to produce all of the difference cells in an animal.
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