 Relatedly, philosophers have also debated the causal distinctiveness of DNA. Consider again the case of cystic fibrosis. A stretch of DNA on chromosome 7 is involved in the process of gene expression, which generates (or fails to generate) the functional product that transports chloride ions. But obviously that final product results from that stretch of DNA as well as all the other developmental resources involved in gene expression, be it in the expression of the functional protein or the dysfunctional one. Thus, a number of authors have argued for a causal parity thesis, wherein all developmental resources involved in the generation of a phenotype such as cystic fibrosis are treated as being on par (Griffiths and Knight 1998; Robert 2004; Stotz 2006).