Organisms are constantly adapting and evolving in response to internal and external stimuli. These changes can arise by either new mutations or by genetic variation that was already present in the system. The latter source of standing genetic variation, which does not affect the usual range of phenotypes, but has a potential to modify a phenotype in the event of an environmental or genetic perturbation, is referred to as cryptic genetic variation (CGV). Studying cryptic genetic variation in present times is especially important. Due to the environmental and cultural changes in recent human history, the uncovering of CGV could be a potential explanation for the rising incidences of “diseases of modernity” (i.e. asthma, diabetes, depression, etc.). We believe that cryptic variants are quite prevalent in the genome and do play a significant part in determining the consequences of genetic perturbations in an organism. To demonstrate the release of CGV, we use the fruit fly, Drosophila melanogaster and perturb the gene, His2Av, which encodes for an alternate histone. Work done in nematode worms and yeast reveal that chromatin regulation may be a factor in suppressing cryptic variation. Additionally, His2Av is the ortholog of yeast HTZ1, which contributes to robustness of cell morphology against microenvironmental variation and has also been shown to have extensive epistasis with genetic variants present in a panel of yeast mutation-accumulation lines. In our study, we have created a new loss-of-function His2Av mutation tagged with GFP and introgressed this mutation via backcrossing into the genetic backgrounds of the Drosophila Genetic Reference Panel (DGRP), which is a panel of naturally-derived inbred D. melanogaster lines. We then crossed each of our introgressed lines to the w[m4] line to reveal dominant effects of the His2Av knockout in different DGRP genetic backgrounds. The w[m4] line has an inversion on the X chromosome that places the white gene responsible for the red pigmentation in fly eyes next to pericentric heterochromatin thereby creating mottled eyes. We are developing a new image-based position effect variegation assay to characterize the extent of variegation in eye pigmentation. By quantifying the amount of variation in perturbed phenotypic responses within and between DGRP lines as well as with and without the His2Av mutation, we can understand the prevalence and behavior of cryptic genetic variation.