Ayah Lababede, an undergraduate student working in the Crown Lab, was among the first place winners for the Fall 2024 Intersections for her poster titled “Two Possible Triggering Mechanisms of pch2-dependent Pachytene Checkpoint That Induce Interchromosomal Effect”. A description of her project is below:

Crossover formation enables the reciprocal exchange of genetic information during prophase 1 of meiosis, which leads to the formation of genetically unique haploid gametes. An interesting phenomenon is observed when there is a heterozygous inversion on a chromosome in Drosophila melanogaster. This phenomenon, the interchromosomal effect (IC), occurs when an inversion on one chromosome suppresses its own crossover formation while increasing crossover formation on other freely recombining chromosomes. Previous research studies have attributed the IC effect to defects in the chromosome axis, which trigger a pch2-dependent pachytene checkpoint activity that delays the progression of prophase 1. However, the type of chromosome axis defect that triggers the checkpoint has not been directly determined. This experiment attempts to address the gap by testing two hypotheses behind the mechanism, which are (1) the checkpoint may be activated by the detection of disrupted axial organization within the chromosome or (2) the checkpoint may be triggered by the absence of a crossover on the inverted chromosome. The inversion selected for this study is inversion AB because it is a medium-sized, single inversion in the middle of the long arm of the X chromosome, which allows us to recover crossovers that occur outside of it. The freely recombining chromosome chosen to observe crossover frequency is chromosome 2. If the detection of disrupted axial organization activates the checkpoint, we would observe significantly increased frequencies of crossovers on chromosome 2 regardless of crossover formation on the X chromosome. If the absence of a crossover on the inverted chromosome activates the checkpoint, we would observe significantly increased frequencies of crossover formation in chromosome 2 when the X chromosome does not have a crossover as compared to when it does have a crossover. Currently, the research question remains unanswered by our work. However, our results suggest that some inversions may not be sufficient to trigger the IC effect and that genetic background plays an important role in influencing crossover frequencies. 

Congratulations Ayah!