In all animals, the mother fills the egg with all the proteins and mRNAs necessary for early development. In Drosophila melanogaster (fruit flies), when one of these genes is missing, it can lead to severe malformations in the larval exoskeleton. The top image is the exoskeleton of a normal embryo where 11 segments are visible as bands of white bristles.  The middle exoskeleton is missing two anterior, thoracic segments.  The bottom embryo is missing the entire head and only has 6 posterior segments; the two eye-like white dots are duplicated tail structures. In the middle and bottom individuals, one gene has been deactivated in the female ovary, resulting in embryos missing one maternal input, which leads to severe defects.

Artwork contributed by Max Staller, a graduate student in Angela DePace’s Lab in the Systems Biology Department at Harvard University