Maternal high-fat diet has a negative impact on fertility—including an apparent direct effect on early development. In this issue, a new study connects this phenotype to depletion of Stella protein in oocytes, demonstrating environmental regulation of a maternal-effect gene.

How maternal diet influences offspring metabolism is unclear, as it is difficult to distinguish between the effects of the in utero environment and epigenetic factors contributed by the oocyte. In a mouse model of high-fat diet, a new study teases apart these mechanisms by using in vitro fertilization and shows that susceptibility of offspring to metabolic disorder can likely be attributed to epigenetic inheritance via the oocyte.

Crossing over, or reciprocal recombination, is essential for accurate segregation of homologous chromosomes at the first meiotic division, resulting in gametes containing the correct chromosome number. A new study in human oocytes analyzes the genome-wide recombination and segregation patterns in all the products of female meiosis, providing experimental support for existing theories about the origin of human aneuploidies and highlighting a novel reverse segregation mechanism of chromosome segregation during meiosis.

Meiotic tetrad analysis is a powerful tool for analyzing all four products of a single meiosis. A new method for tetrad analysis in mammals provides valuable insights into the mechanisms that mediate the exchange of DNA sequences between homologs during meiosis and their influence on the evolution of recombination hotspots.