Editing Forensic entomology (section)

===Gene expression studies===
Although physical characteristics and sizes at various [[instars]] have been used to estimate fly age, a more recent study has been conducted to determine the age of an egg based on the expression of particular genes. This is particularly useful in determining developmental stages that are not evidenced by change in size; such as the egg or pupa and where only a general time interval can be estimated based on the duration of the particular developmental stage. This is done by breaking the stages down into smaller units separated by predictable changed in [[gene expression]].<ref name=Tarone>{{cite journal | vauthors = Tarone AM, Jennings KC, Foran DR | title = Aging blow fly eggs using gene expression: a feasibility study | journal = Journal of Forensic Sciences | volume = 52 | issue = 6 | pages = 1350–1354 | date = November 2007 | pmid = 18093065 | doi = 10.1111/j.1556-4029.2007.00587.x | s2cid = 32533922 | citeseerx = 10.1.1.497.3287 }}</ref> Three genes were measured in an experiment with ''Drosophila melanogaster'': bicoid (bcd), slalom (sll), and chitin synthase (cs). These three genes were used because they are likely to be in varied levels during different times of the egg development process. These genes all share a linear relationship in regards to age of the egg; that is, the older the egg is the more of the particular gene is expressed.<ref name=Tarone/> However, all of the genes are expressed in varying amounts. Different genes on different loci would need to be selected for another fly species. The genes expressions are mapped in a control sample to formulate a developmental chart of the gene expression at certain time intervals. This chart can then be compared to the measured values of gene expression to accurately predict the age of an egg to within two hours with a high [[Confidence interval|confidence level]].<ref name=Tarone/> Even though this technique can be used to estimate the age of an egg, the feasibility and legal acceptance of this must be considered for it to be a widely utilized forensic technique.<ref name=Tarone/> One benefit of this would be that it is like other DNA-based techniques so most labs would be equipped to conduct similar experiments without requiring new capital investment. This style of age determination is in the process of being used to more accurately find the age of the instars and pupa; however, it is much more complicated, as there are more genes being expressed during these stages.<ref name=Tarone/> The hope is that with this and other similar techniques a more accurate PMI can be obtained.