A Quantitative Genetics Model for Morphological Change in Development and Evolution

Abstract

This chapter brings together epigenetic and environmental influences and integrates them with genetic control of development in an approach used to great effect in quantitative genetics. Such an integrative and hierarchical approach is required because there is no oneto-one correspondence between genome and structure, or genotype and phenotype. Indeed, an evolutionary developmental biology is required because (perhaps only because) the genotype does not equal the phenotype.

‘Developmental biologists and geneticists usually focus on different aspects of genes (translation versus transmission). The geneticist uses a particular view of genes as units of heredity (i.e. transmission to the next generation) and may neglect the role of genes in development. Consequently, the developmental biologist may ask whether the distinction between genotype and phenotype advances genetics by leaving out development .Does evolutionary genetics provide a sufficient theory of morphological evolution? The mapping function from genotype to phenotype is not one-to-one. A gene may affect multiple structures (pleiotropy) and traits are often affected by many genes (polygeny). Furthermore, the mapping of gene effects on phenotype may be nonlinear. Because gene action during development is a cyclic series of gene-cell interactions, genes are just one element in the developmental process. Thus the nature of interactions is the primary issue in development.’ Arnold et al., 1989, p. 406; emphasis added