This presentation explores the different types of twins, the biological processes in which the different types of twins are formed, and outlines facts and statistics regarding them.

4. Conjoined Twins: When a pair of monozygotic twins do not separate from each other in early stages, conjoined twins form. Twins are born conjoined often sharing limbs and organs Polar Body Twins : They can be considered half identical. It occurs when the mother’s egg splits before fertilization. Therefore, the twins will share the same genetic traits as their mother and different traits from the father ( as different sperm fertilize one egg that has split). Mirror Image Twins : Occurs when the split of the egg occurs late. The twins often acquire “reverse asymmetric features”. This could mean that a birthmark on one twin can appear exact on the other but on the opposite side ( Hence the mirror image). Only one quarter of monozygotic twins are mirror image twins. Parasitic Twins : It is a form of conjoined twin where one, less developed, small and weaker twin depends on a stronger twin.

5. Average Birth Rate of Various Multiples 2002 - 2005

9. There are many unanswered questions regarding twins. Some individuals believe that such an unexplainable deviation of the typical birth leaves some set of twins with certain abnormal powers ( such as telepathy). Many controlled scientific tests have been conducted to explore the abnormal abilities of twins in which odd occurrences have been noted. Usually both twins are placed in separate rooms. The feelings and reactions of one twin to experimental questions or physical testing are somehow replicated and evident in the other twin who is unaware of what is happening in the other room. These tests would suggest that twins have a biological connection that enables them to feel or think as the other regardless of their proximity to each other. Many argue, however that these tests are not valid and that environmental factors or simply coincidence can explain the oddities.

10. http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Twins_identical_and_fraternal?open http://www.thetwinsalon.com/contact.html http://findarticles.com/p/articles/mi_m0816/is_1991_April/ai_11009335 http://www.twinstuff.com/twinfact1.htm http://www.twinstwice.com/twins.html http://multiples.about.com/od/funfacts/a/twinbirthrate.htm http://www.nomotc.org/index.php?Itemid=55&id=66&option=com_content&task=view http://upload.wikimedia.org/wikipedia/en/thumb/7/7e/Identical-fraternal-sperm-egg.png/300px-Identical-fraternal-sperm-egg.png http://multiples.about.com/od/funfacts/tp/uniquetwins.htm http://farm3.static.flickr.com/2117/2205020974_2c92f92628.jpg?v=0 http://www.theage.com.au/news/world/rare-surgery-to-separate-twins-in-perpetual-hug/2006/08/04/1154198332207.html http://ninjamonkeys.co.za/2005/02/21/parasitic_twin_removed/ http://www.dprogram.com/twin_telepathy.html Graham Twomey Photography