Prenatal survival frequency of reciprocal F1‐hybrids in inbred mice caused both by embryonic factors and genotype of foster mother

摘要

Contents:The prenatal survival frequency of reciprocal F1‐hybrid embryos of C57BL6/J and AKR/J mice differ remarkably (15 us 49) indicating a strong maternal effect. Transfer of the reciprocal F1‐embryos at day 4 p.c. was performed either into foster mothers of their paternal or their maternal strain in order to define the influence of the embryonic plasmatype and the maternal environment on the prenatal survival frequency of those F1‐embryos. The reciprocal F1‐embryos at day 4 p.c. differ according to their mother's strain in numbers of infertitized and degenerated ova, indicating a strong extrachromosomal influence on the prenatal loss, i.e. an influence rather of the embryos themselves than of the maternal environment. The number of implantation sites after transfer of the reciprocal F1‐embryos differs according to the genotype of the foster mother, indicating a stronger influence of the maternal environment during implantation. Despite a small number of live fetuses after transfer, there is a significant difference of healthy fetuses according to the type of the reciprocal F1‐embryos, indicating a stronger influence of the embryos themselves on the post‐impluntative survival frequency. The results support the hypothesis that prenatal loss in isogenic embryos is caused to a heh degree by cytoplasmic facto