Production of monozygotic mouse twins from microsurgically bisected morulae

Mouse monozygotic twins were produced by bisection of the compacted morulae and transfer of the pairs of half-embryos after culture in vitro. The compacted morulae (about 16 cells) were microsurgically bisected, using a fine glass needle attached to a micromanipulator, without any supporting micro-instruments, after pretreatment for zona-softening and decompaction. About 80% of the morulae were bisected without visible cell damage. After 20 h in culture, the half-embryos were classified morphologically as eu-blastocysts, pseudo-blastocysts, or trophectodermal vesicles or non-integrated forms. After culture of 131 pairs of bisected morulae, 75 (57.3%) pairs of eu-blastocysts, 20 (15.3%) pairs comprising a eu-blastocyst and pseudo-blastocyst, and 9 (6.9%) pairs of pseudo-blastocysts, were obtained. The pseudo-blastocysts were considered to be derived from half-morulae in which some blastomeres were destroyed or dissociated as a result of micromanipulation. From 30 pairs of eu-blastocysts transferred to 21 recipients, 5 twin fetuses on Day 17 (18 pairs/9 recipients) and 3 twin male young (12 pairs/12 recipients) were obtained. Survival rate of the twin-embryo pairs was 27.8% at autopsy and 25.0% at term. None of the 20 pairs of pseudo-blastocysts transferred to 10 recipients gave rise to normal conceptuses.     

Trisomy 18 in monozygotic twins

Summary We report a very rare case of a pair of monozygotic twins with trisomy 18 discordant for major anomalies. Our case contributes to published data on the role of nongenetic factors in the etiology of discordance of congenital malformations in genotypically identical twins. We stress the importance of accurate ultrasonic examination in reducing the number of caesarean sections to deliver trisomy 18 infants.     

Assortative mating in monozygotic twins

Abstract

This study investigated assortative mating in a series of monozygotic twins in terms of anthropométrie variables. Initially the twins were analyzed independent of each other, and the results showed fairly clear homogamy among female MZ twins and their spouses, after correcting for age. Further, when stature was partialled out, several anthropometric measures remained significantly correlated. The results for male MZ twins and their spouses were not nearly so clear‐cut. A second analysis treated the co‐twins together, and once again, the female MZ sets tended to show assortative mate choice for stature while the male MZ twins/spouses were not significantly correlated. A follow‐up analysis investigated whether husbands of the female twins were correlated to each other, and negative results were found for all of the 46 anthropometric variables. An apparent contradiction was resolved in the case of stature by regressing spouse stature against that of the co‐twins. It was found that although each of the twins was assortatively mating, one member of the twin set consistently married a taller husband, but the difference was not constant. This had the effect of producing divergent regression lines.     

Ring chromosome 14 in monozygotic twins]

An r(14) is observed in monozygotic twins, with psychomotor retardation and no obvious somatic malformation.     

A case of discordant ptosis in monozygotic twins

Summary A case of discordant ptosis in a pair of monozygotic twins is described. In this context the author surveys the different hypotheses on discordance, and points out the similarity of discordant monozygotic twins and botanical sports and bud-variations.with a pedigree and 3 photosPhotos by courtesy of Professor Dr.G. F. Rochat     

Skeletal development in monozygotic and dizygotic twins]

The maturation and development of 27 monozygotic and 23 dizygotic twins were studied over a 10 year period with data collected at one year intervals from age 9 to adulthood. In this manner the ossification process was recorded based on X-ray films of the carpal bones. Further information was acquired through anthropometric and somatoscopic data reproduced with standard photography. Sex and phase specific genetic factors influencing the maturation process are presented and analysed.