CYP1A1 and obesity due to melanocortin 4 receptor deficiency: These genes have been associated with tumorigenesis and metastasis (in the case of MYO1G, CTNAP2, GFI1, and AHRR), activation of compounds with carcinogenic properties (in the case of CYP1A1 and AHRR), and autism (CNTNAP2), as well as mediating the effect of maternal smoking and birthweight (in the case of GFI1) (Finkelstein, 2017), thereby suggesting a possible epigenetic mechanism linking exposure to smoking during pregnancy with adverse outcomes such as obesity or cancer risk in the offspring.