Behavioural Genetics in the Postgenomics Era

Abstract

There is growing evidence that the complexity of higher organisms does not correlate with the ‘complexity’ of the genome (the human genome contains fewer protein coding genes than corn, and many genes are preserved across species). Rather, complexity is associated with the complexity of the pathways and processes whereby the cell utilises the deoxyribonucleic acid molecule, and much else, in the process of phenotype formation. These processes include the activity of the epigenome, noncoding ribonucleic acids , alternative splicing and post‐translational modifications. Not accidentally, all of these processes appear to be of particular importance for the human brain, the most complex organ in nature. Because these processes can be highly environmentally reactive, they are a key to understanding behavioural plasticity and highlight the importance of the developmental process in explaining behavioural outcomes. Key Concepts: Humans possess fewer protein‐coding genes than maize (i.e. corn) and about the same number as a nematode. There is now strong evidence that the complexity of higher organisms correlates with the relative amount of noncoding RNA rather than the number of protein‐coding genes. Epigenetic processes are key to every aspect of human development from cellular differentiation to learning and memory. Epigenetic mechanisms provide an explanation on the molecular level as to how the pre‐ and postnatal environments can impact offspring's behaviour. Alternative splicing is one mechanism that enables the human body to create over 100 000 proteins with a genome that contains only 20 000 protein coding genes. Each gene in the human genome is not ‘encoded’ for the production of a single protein. Isoforms can have very different and even antithetical physiological effects. Alternative splicing patterns are modulated in response to external stimuli, such as depolarisation of neurons, activation of signal transduction cascades and stress. Post‐translational modification supplements alternative splicing as a means of creating protein diversity with a limited number of protein coding genes. DNA is not the sole biological agent of inheritance.