The entire removal of a JAK and a STAT in Drosophila causes death of Drosophila embryos, whilst mutations in the genes coding for JAKs and STATs can cause deformities in the body patterns of flies, particularly defects in forming body segments.[1] One theory as to how interfering with JAK-STAT signalling might cause these defects is that STATs may directly bind to DNA and promote the transcription of genes involved in forming body segments, and therefore by mutating JAKs or STATs, flies experience segmentation defects.[24] STAT binding sites have been identified on one of these genes, called even-skipped (eve), to support this theory.[25] Of all the segment stripes affected by JAK or STAT mutations, the fifth stripe is affected the most, the exact molecular reasons behind this are still unknown.[22]