Zygosity determination at birth: a plea to the obstetrician.
Explore the source record for details and available documents.
Extraembryonic Membranes↗
Biomedical subjects
C Derom
Publications and source records attributed to C Derom.
Genetic and environmental variation in the birth weight of twins.
Two novel approaches to the analysis of twin data are illustrated with data from birth weight in twins. First, two possible covariates of birth weight are fitted to the data simultaneously, allowing for linear effects of these variables, and their correlation. Second, information on chorionicity is used to estimate the effects of chorion type on birth weight. The data were collected from a large sample of twins born in East Flanders, Belgium. Variation and covariation in twins were considered as a function of sex, chorionicity, maternal age, gestational age, and genotype. No evidence for sex differences in causes of variation was found. As expected, the largest source of variation in bith weight was associated with gestational age. Other common environmental influences were non-significant. Heritability was significant, constituting approximately 40% of variation not associated with maternal and gestational age. A small but significant effect of chorionicity was found, such that dichorionic twins show a greater similarity than monochorionic.
Birth Weight↗
Population-based study of sex proportion in monoamniotic twins.
Explore the source record for details and available documents.
Amnion↗
The validity of Weinberg's rule in the East Flanders Prospective Twin Survey (EFPTS).
Most population studies of twins estimate the number of monozygotic (MZ) and dizygotic (DZ) pairs by Weinberg's differential rule. This rule assumes that within the DZ twins the numbers of unlike-sexed (U) and like-sexed (L) twins are equal. The literature on the validity of Weinberg's rule is still controversial. In this prospective population-based study (EFPTS) of 2,589 twin pairs, of whom 2,577 were of known zygosity and placentation, the estimates of Weinberg's rule agree well with the results of direct zygosity determination.
Belgium↗
The European Multiple Birth Study (EMBS).
The more that twin and other multiple pregnancies are investigated, the more it becomes mandatory that collaborative studies are set up in order to attain the critical number of cases needed to achieve meaningful and reliable results. The European Multiple Birth Study (EMBS) aims to study two aspects of twin and multiple pregnancy: 1) management of pregnancy and labour, with emphasis on the prevention of preterm delivery; 2) accurate determination of zygosity, a prerequisite for the proper use of the twin method in a variety of fields, eg, congenital malformations, genetics, clinical investigations, etc. The rationale, the methods and the organisation of the study are described and discussed.
Data Collection↗
Increased monozygotic twinning rate after ovulation induction.
Multiple births after artificial induction of ovulation (AIO) are usually considered to be due to fertilisation of multiple ova. In the East Flanders Prospective Twin Study between 1978 and 1985 the frequency of zygotic splitting after AIO (1.2%) was significantly higher than the expected frequency (0.45%) among spontaneous twins and triplets. Moreover, after AIO the frequency of zygotic division was significantly higher in triplets than in twins. AIO seems to be the first identified biological mechanism influencing the monozygotic twinning rate.
Female↗
Zygosity determination in newborn twins using DNA variants.
A prerequisite for the optimal use of the twin method in human genetics is an accurate determination of the zygosity at birth. This diagnosis is sometimes hampered by the lack of available specific markers. We report here the use of DNA variants (restriction fragment length polymorphisms) as genetic markers for zygosity determination. We have analysed the placental DNA of 22 twin pairs with known zygosity on Southern blots by hybridisation with polymorphic human DNA probes. We looked at six different polymorphic sites using four restriction enzymes and six DNA probes. Among 10 dizygotic (DZ) pairs, only one was not demonstrably different and seven had at least two discordances. Within each of the 12 monozygotic (MZ) pairs there was complete concordance. Thus, nine of 10 dizygotic and 12 of 12 monozygotic twins were assigned their correct zygosity solely by comparison of six DNA variants. The use of these highly polymorphic DNA probes may have practical importance for antenatal diagnosis and paternity testing.
DNA Restriction Enzymes↗
High-level synthesis in Escherichia coli of the SV40 small-t antigen under control of the bacteriophage lambda pL promoter.
Several plasmids were constructed in which the SV40 small-t antigen gene was inserted in close proximity downstream from the thermoinducible leftward promoter (pL) of bacteriophage lambda. Upon temperature induction the best of our constructions expressed a small-t-related 19 000-dalton polypeptide in an amount corresponding to approx. 2.5% of total de novo protein synthesis. This 19 000-dalton protein was identified as small-t by specific immunoprecipitation with anti-T serum and by two-dimensional fingerprint analysis. In addition to the 19 000-dalton product, representative plasmids expressed fairly large amounts (up to 7% of total de novo protein synthesis) of a protein with an apparent Mr of 14 500. This 14 500-dalton polypeptide was shown to be related to authentic small-t. Presumably the secondary structure of the mRNA starting at pL is such that translation initiation at an internal AUG codon of the small-t gene is favored over initiation at the true initiating codon.
Antibody Specificity↗
Systematic alteration of the nucleotide sequence preceding the translation initiation codon and the effects on bacterial expression of the cloned SV40 small-t antigen gene.
In the preceding paper (Derom et al., 1981) we described the cloning in bacterial plasmids of the simian virus 40 (SV40) small-t antigen gene under transcriptional control of the bacteriophage lambda pL promoter. Systematic variation of the distance and/or nucleotide sequence between the Shine-Dalgarno ribosome interaction sequence and the small-t translation initiation codon leads to considerable differences in production of small-t by the different plasmids. Secondary structure models derived for the different mRNAs confirm our previous conclusions about the requirement first for an accessible start codon and second for an accessible ribosome interaction site for efficient translation initiation. Secondary structure models for mRNAs from plasmids containing the small-t gene under control of the lac promoter are in agreement with these conclusions.
Antigens, Viral↗