An epidemiological study of genetic markers in a sample of 111 pairs of twins and their parents. In this sample an estimate is available of the timing of conception in relation to ovulation, calculated from a knowledge of the characteristics of the menstrual cycle and the date of resumption of intercourse following the menstrual Jewish ritual sexual separation. Of the twins, 43 were born from conceptions occurring """"""""late"""""""" in relation to the estimated day of ovulation and, therefore, probably from overripe ova. The remaining twins appeared to have been conceived normally. The objective is to determine why twinning was so markedly increased in the """"""""late"""""""" fertilizations and to test the hypothesis that this is due to a third type of twinning, uniovular dispermatic, following the premature division of the ovum prior to fertilization. The investigators will test blood groups, HLA phenotypes, isoenzymes, nucleolar organizing regions (NORs) and chromosome C- and Q-bands. They will detect uniovular dispermatic twinning if the twins are concordant for all alleles received from the mother, while partially discordant for those received from the father. They will also develop mathematical models for estimating the probability of detecting first and second polar body twins and for distinguishing them from dizygous sets. They may also detect polar body twinning. Existence of a third type of twinning would necessitate a reappraisal of the theoretical and mathematical basis for heritability studies in genetic epidemiology. Although geneticists have long postulated the existence of uniovular dispermatic and polar body twins, and have suggested that they are more likely to occur after fertilization of overripe ova, no systematic search has ever been made for them before.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD019597-02
Application #
3316999
Study Section
Epidemiology and Disease Control Subcommittee 3 (EDC)
Project Start
1985-06-01
Project End
1987-05-31
Budget Start
1986-06-01
Budget End
1987-05-31
Support Year
2
Fiscal Year
1986
Total Cost
Indirect Cost
Name
Hebrew University of Jerusalem
Department
Type
DUNS #
600044978
City
Jerusalem
State
Country
Israel
Zip Code
91904
Shahar, S; Morton, N E (1986) Origin of teratomas and twins. Hum Genet 74:215-8