Changes in gene expression are among the major causes of phenotypic and morphological differences within and between species as well as between diseased and healthy tissues. In eukaryotes gene expression is regulated at different levels. Transcriptional gene regulation is the most conserved and most regulated level of gene expression and is mediated by DNA binding proteins called transcription factors. Transcription factors are multidomain proteins with mostly conserved and structured DNA binding domains and less conserved and disordered effector domains. While DNA binding domains recognize specific motifs which are usually 6-12 bp long, effector domains’ roles are variable. They mediate target recognition and transcription specificity through promiscuous and weak DNA binding, interact with cofactors and transcription machinery, confer inducibility to transcription factors by providing platform for most of the post-translational modifications. We investigate how these different structural regions and mechanisms impact robust and specific transcriptional regulation and development by using in vitro biochemical assays and in vivo during Drosophila embryogenesis.