 In terms of development, the genome has been described not only as a resource, but also as reactive to the cellular context rather than as directing cellular processes (S. Gilbert 2003; Griffiths &amp; Stotz 2013: Ch. 4; Keller 2014). The genome is always embedded in a cellular environment (also virus genomes become reactive in the context of their host’s cells), and cellular processes mediate between the organismal or extra-organismal environment and the genome. The post-genomic gene concept is thus open to integrate molecular epigenetic processes that turn environmental cues into regulatory signals. Molecular epigenetics has also been discussed as a pathway of inheritance, alternative to DNA transmission and more responsive to environmental changes (Jablonka &amp; Raz 2009; entry on  inheritance systems).  Emerging knowledge of these processes re-shapes explanations in heredity, development, and evolution and hence shifts the explanatory status of gene concepts (Baedke 2018; Griesemer 2011; Griffiths &amp; Stotz 2013, Ch. 5; Le Goff et al. 2021; Stotz &amp; Griffiths 2016). Furthermore, next to the complexity of the regulation and genesis of molecular products, also the interaction of products as studied in systems biology displays a complexity that makes it difficult to ascribe functional roles to genes (see entry on  philosophy of systems and synthetic biology;  see  §1.5).  If genes are deleted from the genome experimentally (“gene knock-out”), this often does not have the expected effect on developmental processes, because the encoded molecules are part of large interaction networks that can exhibit a high degree of robustness and redundancy (Mitchell 2009: Ch. 4; Morange 2001: Ch. 5). The stochasticity of gene expression and molecular interactions emerges as another aspect complicating the role of genes and gene products in cellular processes (Casali &amp; Merlin 2020; Kupiec 2014; Morange 2011; Nicholson 2019).