| MadSci Network: Genetics |
Well, unlike identical twins which arise from the spliting of a single
fertilized egg, fraternal twins arise from two different fertilized eggs
(i.e. each fertilized by a different sperm). These separate fertalized eggs
have the same genetic relatedness as ordinary siblings (brothers and
sisters). Thus only half of the genes in the twins are identical.
Basically fraternal twins are no different than two siblings born
several years apart. It was just that 2 eggs were released into the
fallopian tube of the female instead of one.
Hope this helps!
-Mike
Reference:
Hartl DL, Jones EW (1998) Genetics : principles and analysis. Jones and
Bartlett Publishers, Sudbury, Mass. pp 682.
Try the links in the MadSci Library for more information on Genetics.