Somatic cell nuclear transfer (SCNT)

SCNT is a laboratory technique for creating an ovum with donor nucleus. In it, nucleus containing the organism’s DNA of somatic cell (a body cell other than sperm or egg cell) is removed and rest of cell discarded. The nucleus of somatic cell is then inserted into enucleated egg cell which reprograms somatic cell nucleus by the host cell. The egg, now containing nucleus of somatic cell, is stimulated with a shock and will begin to divide forming blastocyst (an early stage embryo with about 100 cells) with almost identical DNA to original organism. It can be used in embryonic stem cell research, regenerative medicine i.e. “therapeutic cloning.” It can also be used as first step in process of reproductive cloning. Reproductive cloning occurs by implanting SCNT derived blastocyst into the uterus of a surrogate mother where the embryo develops into fetus. Mouse, Monkey and Human embryonic stem cells can be created using SCNT. This technique was used to create first cloned mammal, Dolly the sheep. 

Advantage 

  1. It can be used to produce stem cells. 
  2. It has the potential to produce extinct species e.g cells collected from wooly mammoth could be used as nuclear donors for enucleated elephant eggs. This has been proved by an experiment on mice. Mice were cloned using somatic cell nuclei derived from mouse that had been frozen for more than 15 years. 
  3. SCNT can be used to generate exact copies of cells to be used for tissue and organs for a patient in need. If this is accomplished, it could potentially eliminate the desperate need for donor organs around the world. 
  4. If SCNT were to be mastered by humans, it could assist in treating diseases associated with mitochondrial dna. This is because the nucleus of a somatic cell burdened with one of these diseases and that undergoes somatic cell nuclear transfer prevents mitochondrial dna mutations. 

Disadvantage

  1. It is inefficient process with majority of studies reporting between 0.5-5% develop correctly. Loss of fetuses and young occur throughout gestation,  at birth and following birth with a range of developmental abnormalities being reported. Reasons for these abnormalities occuring is unknown but may reflect incomplete or inappropriate reprogramming.
  2. There is a high fetal death rate when SCNT is used on an embryo in any organism. 
  3. The clones are not exact copy (100% copy)  of desired or donor species as it contains the cytoplasmic traits of eggs. 

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