Asexual Reproduction: Somatic Cell Nuclear Transfer

Cloning (clonal expansion) is the production of genetically identical individuals with existing individuals. This process is called somatic cell nuclear transfer. Scientists take mature unfertilized eggs and remove their nucleus. Next, they introduce nuclei obtained from specialized (somatic) cells of adult organisms. When the egg begins to divide, they transplant embryos into the female uterus to begin pregnancy. Re-nucleated eggs are identical to organisms that are genetically a source of import nuclei as almost all genetic material of cells is contained in their nuclei (Kass, 2001).

H. R. 2505 specifically prohibits "asexual reproduction" achieved through "somatic cell nuclear transfer" technology, which is used to produce dolly. This method can be used for scientific and medically useful cloning such as cloning of DNA fragments (molecular cloning), replication of tissues or cells in culture (cell cloning), or entire organisms of non-human animals or embryos I do not forbid the technique. This bill also prohibits laboratory customs such as parthenogenesis and "pairing".

Reproductive cloning usually creates genetically identical animals using "somatic cell nuclear transfer" (SCNT). This process requires transplantation of nuclei from donor adult cells (somatic cells) to nucleus-removed eggs, or transplantation of cells from blastocysts from which nuclei have been removed. If the egg begins to split normally, it is transferred to the womb of the surrogate mother. Since somatic cells may contain mutations in their nuclear DNA, these clones are not exactly identical. In addition, the mitochondrial genome is different from the nuclear donor cells in which it is produced, as mitochondria in the cytoplasm also contain DNA and the mitochondrial DNA is completely derived from cytoplasmic donor eggs during SCNT. This may be important for heterogeneous nuclear transplant where nuclear-mitochondrial incompatibility can lead to death.

Somatic cell nuclear transfer (SCNT) also known as nuclear transplantation uses somatic cells. Somatic cells are any cells of the body other than sperm and eggs, both of which are germ cells. Germ cells are also called reproductive cells. In mammals, each somatic cell has two sets of chromosomes, but the germ cell has only one set of chromosomes. SCNT also uses nuclei, which are compartments that hold cellular DNA. DNA is divided into packages called chromosomes, which contain all the information necessary to form organisms. A small difference in our DNA makes each one of us unique.

Reproductive cloning refers to eggs that undergo nuclear transplant of somatic cells and allow the resulting cells to grow into infants that are accurate genetic copies of somatic cell donors. Attempting reproductive cloning is error prone and inefficient, and most clones fail. The most famous clone, Dolly (sheep), was created after a number of trials and failures, after which the lifespan was shortened (Wilmut et al., 1997). In February 1997, Dr. Ian Wilmut announced the establishment of the first cloned mammal. A report published in Nature describes Dolly, a lamb cloned using somatic cell nuclear transfer (SCNT). This groundbreaking paper and the attention of the media it received caused direct reactions from Washington DC public and politicians. And they are worried that the use of this technology may clone humans.