Why is that during somatic cell nuclear transfer the embryo is never implanted into the uterus?

During somatic cell nuclear transfer (SCNT), a cloning technique, the embryo that is formed is not typically implanted into the uterus. This is because the purpose of SCNT is often for research purposes or reproductive cloning, rather than for establishing a pregnancy.

SCNT involves the removal of the nucleus from an egg cell and replacing it with the nucleus of a somatic (body) cell, which could be taken from any part of an individual's body. The resulting embryo has the same genetic information as the individual who donated the somatic cell. However, there are several reasons why the embryo is not typically implanted:

1. Ethical considerations: There are various ethical debates surrounding reproductive cloning, which involves creating a cloned human embryo and implanting it to develop into a full-term fetus. Due to these ethical concerns, human reproductive cloning is largely prohibited in many countries, including for research purposes.

2. Safety concerns: Somatic cell nuclear transfer is a complex and delicate procedure, and the success rates can be low. The resulting embryos may have abnormalities or developmental issues that make them unsuitable for implantation. Additionally, there is a risk of complications during pregnancy and potential harm to the surrogate mother.

3. Research purposes: SCNT is commonly used for research, such as studying cellular reprogramming, genetic diseases, or developing stem cell lines. By not implanting the embryos, scientists can study them in a controlled laboratory environment without ethical or safety concerns.

It's important to note, however, that SCNT has been successfully used in the past for reproductive cloning in animals, such as with Dolly the sheep. But the same ethical and safety concerns apply to the cloning of animals as well.

Overall, the decision to not implant the embryo in SCNT is primarily driven by ethical considerations, safety concerns, and the purpose of the specific procedure, whether it be research or reproductive cloning.