Demystifying Medicine Video

This video presents information about a newly discovered third type of twin whose genetic similarity exists somewhere between fraternal and identical twins: semi-identical twins. Two cases of sesquizygotic twins have been reported in the literature, one in 2007 and the other in 2019, where the twins were found to be identical on their mother's side but not the father's side. The video examines the most plausible theory of how semi-identical twins occur. It also provides insight into the difference between sesquizygotic and monozygotic twins as well as dizygotic twins.

[Please complete our feedback form]

  • Gabbett, M. T., Laporte, J., Sekar, R., Nandini, A., McGrath, P., Sapkota, Y., ... & Chiu, R. (2019). Molecular Support for Heterogonesis Resulting in Sesquizygotic Twinning. New England Journal of Medicine, 380(9), 842-849.
  • Masters (2007). A New Kind of Twin. Time.
  • Souter, V. L., Parisi, M. A., Nyholt, D. R., Kapur, R. P., Henders, A. K., Opheim, K. E., . . . Montgomery, G. W. (2006). A case of true hermaphroditism reveals an unusual mechanism of twinning. Human Genetics,121(2), 179-185. doi:10.1007/s00439-006-0279-x