[Analysis of the effect of the loop-tail gene in mouse embryos].

Mitotic index and parameters of the cell cycle were determined in the brain and spinal cord of 10 days old Lp/Lp and +/+ mouse embryos. The mitotic index and duration of the cell cycle periods proved to be the same for embryos of both the genotypes. The generation time of the brain and spinal cord cells both in the mutant and normal embryos is 9 hrs, durations of S- and G2-periods 6 and 1, resp., and the total duration of G1- and M-periods 2. The gene Lp does not interact with the gene Sp in double heterozygotes. The gene Lp does not manifest itself in the cells of differentiating central nervous system and the failure of the neural tube closure is not due to the changes in the proliferative activity of its cells and is a secondary gene effect.