Fraternal Twins

Fraternal twins are also dizygotic twins. They result from the fertilization of two separate eggs during the same pregnancy. Fraternal twins may be of the same or different sexes. They share half of their genes just like any other siblings. In contrast, twins that result from the fertilization of a single egg that then splits in two are called monozygotic, or identical, twins. Identical twins share all of their genes and are always the same sex. Courtesy: National Human Genome Research Institute

biology | cell | fertilization | egg | twins

View and download full-sized image.
Source: .
http://www.genome.gov/
License: Public Domain. If you are going to redistribute this image online, a hyperlink to the above source page is mandatory.