Student Theses and Dissertations

Date of Award

Spring 2018

Document Type


Degree Name

Bachelor of Arts (BA)

Honors Designation


Program of Study




First Advisor

Rebecca F. Spokony

Second Advisor

Helen Eisenman Barbour

Third Advisor

Krista Dobi


Crystal cells are one of three requisite hemocytes that take part in fighting infection and wound healing in Drosophila melanogaster (common fruit flies). The developmental genetics of crystal cell formation is only beginning to be discovered. To address this question, we performed a Genome-Wide Association Study (GWAS) on larval crystal cell number from 78 isolines of the Drosophila Genetic Reference Panel (DGRP) collection. The DGRP consists of naturally caught fruit flies that are inbred to near homozygosity with completely sequenced genomes. By placing the wandering third instar larvae under heatshock, a process that induces the melanization of crystal cells, it was possible to manually score the number of black crystal cells throughout the larvae. We discovered that the average number of crystal cells in each DGRP line (10 larvae per line) varied, ranging from 0 to 730. The average of all the crystal cells counted (all DGRP lines collectively) was calculated to be 220. Also, of the 78 DGRP lines, 75 of them had more crystal cells when compared to the Oregon-R control line (with a mean of 20 crystal cells per larvae). GWAS of the DGRP crystal cell count data found 128 polymorphisms (p<10-5) that may be associated with differences in crystal cell number between the lines. From the list of polymorphisms, we chose to test 10 genes (with smaller p-values) mapped to the polymorphisms. However, overexpression was done for 4 of the 10 genes. Overexpressing 3 of the 4 genes led to altered crystal cell number. In total, we have found 3 new genes (domino, extra-extra, and hemese) involved in crystal cell development.


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