From single gene to phenotype: questioning a discrete gene in explaining phenotype diversity

Abstract

The great diversity of phenotypes across organisms raises the question of how it emerged from the digital DNA sequence. Often the question is summarized as ‘how many genes do we really need?’ The benefit of answering this is readily apparent; particularly since sequencing the genome, research has sought the origin of normative and pathological phenotypes in our genes. However, in response, the literature will retort that neither the number of genes nor the size of the genome make robust predictions about phenotype complexity or diversity. For example, a common sea flea, Daphnia pulex, has ~31,000 genes, compared with our ~23,000. Given the gene-centric state of current biology, the questions these comparisons advance about the power of the gene are disconcerting. The remit of what follows is to address the value of quantifying genes to explain the phenotype. The heterogeneous nature of gene definitions in the literature necessitates brief discussion of gene ontology. Following this, I will discuss how function emerges from the transcript, and the resultant translated functional product. However, questioning the power of the gene should be taken in tandem with questioning its scope; this discussion will end on a brief survey of the proportion of the phenotype that should readily be attributed to non-DNA inheritance information, which highlights the need or systems-based approaches to phenotype variability.