When the same sex intended parents are both male, the sperm from either one or both of the partners will be combined with eggs from an egg donor which then develop into embryos. (surrogateparenting.com)
This is the result of a genetic error the leads to the tissue not developing into an embryo. (checkpregnancy.com)
Differentiation occurs as a few fertilized cells develop into an embryo acquire the specialized organs that will be needed later in life. (sciencenewsforstudents.org)