How are cloned embryos produced using somatic-cell nuclear transfer?

Sourav PanNovember 8, 2024

Answered

Cloned embryos are produced using a technique known as somatic cell nuclear transfer (SCNT). This method involves several key steps to transfer the nucleus of a somatic cell into an enucleated egg cell, leading to the development of a cloned embryo. Here’s a detailed breakdown of the SCNT process:

Steps in Producing Cloned Embryos via SCNT

1. Cell Selection:
   • A somatic cell is obtained from a donor organism. This could be any differentiated cell type, such as skin or muscle cells, which contain the complete genetic material of the donor.
2. Enucleation:
   • An egg cell (oocyte) is harvested from a female donor of the same species. The nucleus of this egg cell, which contains its genetic material, is removed through a process called enucleation. This creates an enucleated egg, or cytoplast, which is devoid of its original genetic information.
3. Nuclear Transfer:
   • The nucleus from the selected somatic cell is then introduced into the enucleated egg cell. This can be done by injecting the somatic nucleus directly into the cytoplasm of the egg or placing it in the peri-vitelline space (the space between the egg membrane and cytoplasm).
4. Cell Fusion:
   • To facilitate the integration of the somatic nucleus into the egg cell, electrical pulses or chemical treatments are applied. These stimuli help fuse the two cells together and initiate cellular activation.
5. Activation:
   • Following fusion, the newly formed cell (now containing the somatic nucleus) must be activated to begin dividing and developing into an embryo. This activation can be achieved through electrical stimulation or chemical agents that mimic fertilization signals.
6. Embryonic Development:
   • Once activated, the cell begins to divide and develop into a multicellular embryo (blastocyst stage). This embryo can then be cultured in vitro for further development or implanted into a surrogate mother’s uterus for gestation.
7. Implantation:
   • If the goal is reproductive cloning, the developing embryo is implanted into a surrogate mother where it can develop into a full organism that is genetically identical to the original donor organism from which the somatic cell was taken