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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.

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  1. 2. <ul><li>Identical Twins </li></ul><ul><li>Certain biological processes determine if a set of twins can be considered “ Identical” ( also known as Monozygotic). </li></ul><ul><li>For Identical twins to be born the mother’s egg is fertilized by one sperm and the egg proceeds to split in half. </li></ul><ul><li>Identical twins can therefore only be same gendered </li></ul><ul><li>Identical twins normally appear to be exactly alike at birth. </li></ul><ul><li>about 33% of all twins born are identical </li></ul>
  2. 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.
  3. 5. Average Birth Rate of Various Multiples 2002 - 2005
  4. 8. <ul><li>There are approximately 125 million twins currently in the world. </li></ul><ul><li>Twins born in china many years ago were considered bad luck and shameful and were killed </li></ul><ul><li>an explanation for a high twin birth rate in Africa has to do with dietary foods. For example, yams act as a natural fertility drug. </li></ul><ul><li>the oldest living twins recorded according to the Guinness World Records are the Phipps twins. Eli Phipps died at the age of 108 and his brother died at the age of 113. </li></ul><ul><li>The longest living conjoined twins are Chang and Eng Bunker and died at the age of 63. </li></ul>
  5. 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.
  6. 10. Graham Twomey Photography