[Selection for fertility under gestagen synchronization of estrus in mice]

The results of selection of mice for the selection index, with the use of gestagenic synchronization of oestrus for 12 generations, allows to affirm that: The synchronization effect decreases with successive generations, which is connected with the existence of a negative correlation between the synchronizability and fertility. The selection effect in the control population was higher than that in experimental one, subjected to oestrus synchronization. It can be supposed that gestagen dimishes the correlation between the genotype and the phenotype, thus decreasing the selection efficiency in the experimental population. A similar tendency was found for the number of implantations and litter size at the age of 1, 10 and 21 days after birth.