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The topic of reproductive cloning became a much larger public issue with the announcement that Dolly, a sheep clone who was genetically identical to her cell-donor, was born at the Roslin Institue in Scotland (4).

Every cell in our body contains the genetic coding of our entire physical make-up. However, during the process of fetal development, only one of the thousands of characteristics encoded on the DNA strand is "silenced" (4). In a process called "somatic cell nuclear transfer" (SCNT), scientists transfer genetic material from the nucleus of a donor adult cell (i.e.: a cell from Dolly's mammary gland) that has been reprogrammed to express all of the genetic characteristics to an egg whose nucleus, and thus its genetic material, has been removed. The reconstructed egg containing the DNA from a donor cell must be treated with chemicals or electric current in order to stimulate cell division. Once the cloned embryo reaches a suitable stage, it is transferred to the uterus of a female host where it continues to develop until birth (1). Thus, a new creature is able to fully develop from this single cell. While this creature may seem to be almost identical to its donor, some genetic material comes from the mitochondria in the cytoplasm of the enucleated egg. This means that the host mother will contribute a few characteristics to the clone.

   There are 3 main steps to reproductive cloning:
      -All of the DNA is removed from a female's egg. The egg is now hollow and does
      not contribute to any of the genetic characteristics.
      -Nuclear Transplantation: Another adult cell which has been "re-activated" is
      now fused into the hollow egg by means of electric current.
      -The fertilized egg is implanted into the womb of another female (surrogate mother)
      and the fetus develops through a normal gestation period (4).

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In sexual reproduction a child gets half its genes from its mother (in her egg) and half from its father (in his sperm). The process of sexual reproduction is shown below:

(4)

This specific type of cloning is an asexual form of reproduction. All the child's genes would come from a body cell of a single individual. See the image below for a better understanding:

(4)