This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2025. The fellowship supports research and training of the fellow that will contribute to biology in innovative ways. Mucus serves a critical protective role throughout the human body, forming barriers on organs exposed to external environments such as the lungs, stomach, and reproductive tissues. This protective function is primarily mediated by specialized proteins known as mucins, characterized by long, repetitive segments extensively covered with sugar molecules essential for their function. Recent advances in DNA sequencing now enable precise investigation of these repeats at the genetic level. This research focuses on mucin-1 (MUC1), a crucial component of the mucus barrier in the uterus. MUC1 acts as a gatekeeper for pregnancy as successful implantation of a fertilized embryo into the uterine wall requires the reduction of this barrier. The number of repeat segments within the MUC1 gene are known to vary substantially between individuals, influencing the size of the resulting MUC1 protein. However, the impact of this genetic variation on the structure of the attached sugars, the mucus barrier, and pregnancy remains unexplored. By examining how variations in these repeats affect the structural and functional properties of the MUC1 protein, this project aims to deepen our understanding of complex genetic and protein variations, ultimately shedding new light on human evolution and pregnancy biolog