Explain how stem cells obtained from IVF leftovers and somatic cell nuclear transfer differ in terms of the sources of their genomes. Solution Oocytes from women were extracted and inseminated with thaed donor sperm, after the process of insemination oocytes were successfully fertilized and developed into blastocyst stage and the inner cell masses of the blastocyst that were removed yielded stem cell lines. From a left over IVF, extraction of single blastomere is helpful. In somatic cell nuclear transfer, the nucleus of a somatic cell is transferred to the cytoplasm of an ennucleated egg which then becomes a zygote and is then allowed to develop to blastocyst stage. Reference 1. Josefson, D. (2001). Embryos created for stem cell research.British medical journal, 323(7305), 127..