Date: June 2015.
Source: Twin Research and Human Genetics, Volume 18, Issue 03, pp 306-313.
Abstract: The aim of this study was to compare facial 3D analysis to DNA testing in twin zygosity determinations. Facial 3D images of 106 pairs of young adult Lithuanian twins were taken with a stereophotogrammetric device (3dMD, Atlanta, Georgia) and zygosity was determined according to similarity of facial form. Statistical pattern recognition methodology was used for classification. The results showed that in 75% to 90% of the cases, zygosity determinations were similar to DNA-based results. There were 81 different classification scenarios, including 3 groups, 3 features, 3 different scaling methods, and 3 threshold levels. It appeared that coincidence with 0.5 mm tolerance is the most suitable feature for classification. Also, leaving out scaling improves results in most cases. Scaling was expected to equalize the magnitude of differences and therefore lead to better recognition performance. Still, better classification features and a more effective scaling method or classification in different facial areas could further improve the results. In most of the cases, male pair zygosity recognition was at a higher level compared with females. Erroneously classified twin pairs appear to be obvious outliers in the sample. In particular, faces of young dizygotic (DZ) twins may be so similar that it is very hard to define a feature that would help classify the pair as DZ. Correspondingly, monozygotic (MZ) twins may have faces with quite different shapes. Such anomalous twin pairs are interesting exceptions, but they form a considerable portion in both zygosity groups.
Article: Comparing Facial 3D Analysis With DNA Testing to Determine Zygosities of Twins.
Authors: Ville Vuollo, Mantas Sidlauskas, Antanas Sidlauskas, Virpi Harila, Loreta Salomskiene, Alexei Zhurov, Lasse Holmström, Pertti Pirttiniemi, and Tuomo Heikkinen. Institute of Dentistry, University of Oulu; Medical Research Center Oulu, Oulu University Hospital; and Department of Mathematical Sciences, University of Oulu in Oulu, Finland; Clinic of Orthodontics, Lithuanian University of Health Sciences and Institute of Biology Systems and Genetics, Veterinary Academy, Lithuanian University of Health Sciences, in Kaunas, Lithuania; and the Institute of Dentistry, University of Cardiff, Cardiff, UK.