Re: Do Identical Twins have to have the same blood type to be Identical?

Bridget,

Identical twins do have the same blood type and you and yours sisted do.  
However, the Rh factor (positive or negative) may not be the same.  An 
Identical twin is defined when a single ovum is fertilized by a single 
sperm followed by cell division.  Therefore identical siblings are 
genetically identical.  The Rh factor or antigen D is either absent or 
present in red blood cells.  This is important to know because someone who 
is negative should never receive positive blood because they may have 
antibodes against the Rh antigen.  So if you are positive you may not give 
a transfusion to your sister if she is negative.

Sources
"Human Physiology" by Rhoades and Pflanzer 3rd edition
The Learning Channel Website

Sincerely,


Mike