"When under the control of one alter, they may exhibit different behaviors, mannerisms, personalities, gender orientation, and physical properties (such as handedness, allergies and eyesight)..."

http://www.medicinenet.com/script/main/art.asp?articlekey=38077



"One of the most baffling mysteries of multiple personality disorder is how alternate personalities can sometimes show very different biological characteristics from the host and from each other. Several personalities sharing one body may have different heart rates, blood pressures, body temperatures, pain tolerances, and eyesight abilities."

http://science.jrank.org/pages/4497/Multiple-Personality-Disorder-Symptoms.html


This is nothing out of the norm for multiples and it has been known for a long long time.

The question then arises "Is it possible it is not purely physical?"

Science shows that are genes are influenced and turn off and on by environment, thoughts and emotions etc...

Bruce Lipton has done some great work on genes etc He worked for years on the cloning projects. "Biology Of Belief" is a very good book of his and his site has some very interesting articles on quantum physics and how we effect our genes etc

http://www.brucelipton.com/

Course, stepping away from the dogma leaves him open to ridicule...