BACKGROUND: While it is generally accepted that monozygotic (MZ) twins are identical with respect to inherited traits, because they share 100% of their genetic material, clinical findings and scientific evidence does not support this belief. In addition to environmental factors and stochastic developmental events, a number of genetic mechanisms, detectable by new techniques in molecular genetics, explain the differences frequently observed in MZ twins. CASE REPORT: Nine-year-old twin girls requested treatment for a dental malocclusion. Their facial and occlusal features were very similar. Panoramic radiographs revealed hypodontia of two permanent teeth in one twin (35 and 45) and of only one tooth in the other (45). An incorrect diagnosis of dizygosity (DZ) had been made at birth based on the presence of two amniotic sacs. Despite discordance in the dental complement of both girls their orthodontist suspected that the twins might be identical. A genetic study performed by quantitative fluorescence-polymerase chain reaction (QFPCR) analysis of chromosomes 13, 15, 16, 18, 21, 22, and X confirmed that the twins were MZ. CONCLUSION: Discordances in dental complement between MZ twins are not uncommon and do not exclude monozygosity.
BACKGROUND: While it is generally accepted that monozygotic (MZ) twins are identical with respect to inherited traits, because they share 100% of their genetic material, clinical findings and scientific evidence does not support this belief. In addition to environmental factors and stochastic developmental events, a number of genetic mechanisms, detectable by new techniques in molecular genetics, explain the differences frequently observed in MZ twins. CASE REPORT: Nine-year-old twin girls requested treatment for a dental malocclusion. Their facial and occlusal features were very similar. Panoramic radiographs revealed hypodontia of two permanent teeth in one twin (35 and 45) and of only one tooth in the other (45). An incorrect diagnosis of dizygosity (DZ) had been made at birth based on the presence of two amniotic sacs. Despite discordance in the dental complement of both girls their orthodontist suspected that the twins might be identical. A genetic study performed by quantitative fluorescence-polymerase chain reaction (QFPCR) analysis of chromosomes 13, 15, 16, 18, 21, 22, and X confirmed that the twins were MZ. CONCLUSION: Discordances in dental complement between MZ twins are not uncommon and do not exclude monozygosity.
Authors: Bart J Polder; Martin A Van't Hof; Frans P G M Van der Linden; Anne M Kuijpers-Jagtman Journal: Community Dent Oral Epidemiol Date: 2004-06 Impact factor: 3.383
Authors: Mario F Fraga; Esteban Ballestar; Maria F Paz; Santiago Ropero; Fernando Setien; Maria L Ballestar; Damia Heine-Suñer; Juan C Cigudosa; Miguel Urioste; Javier Benitez; Manuel Boix-Chornet; Abel Sanchez-Aguilera; Charlotte Ling; Emma Carlsson; Pernille Poulsen; Allan Vaag; Zarko Stephan; Tim D Spector; Yue-Zhong Wu; Christoph Plass; Manel Esteller Journal: Proc Natl Acad Sci U S A Date: 2005-07-11 Impact factor: 11.205