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NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Identical-Fraternal Twinning 
Name: Pat
Status: Student
Age: N/A
Location: N/A
Country: N/A
Date: December 2004
Question:
I read your explanation of conjoined/identical twins. When I had my 'identical' twins 20 years ago, there was speculation in the medical field that there is another state of twinsome they were referring to as "identical-fraternal", whereby one egg splits but is fertilized AFTER the split by two sperm. The result is 'identicals' that are not so identical. Can you elaborate on this?


Replies:
In order for the egg to split it must first be fertilized by a sperm. Each resulting cell receives a complete set of chromosomes, half maternal and half paternal, so there won't be anymore sperm entering these cells even if they completely separate from each other to produce identical twins.

Ron Baker, Ph.D.


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