| Gene duplication is thought to play the singular most important role in the formation of novel genes. Yet, the early evolutionary dynamics of gene duplicates are obscure. In order to elucidate the structural characteristics and subsequent evolutionary properties of newborn gene duplicates, a large sample of young gene duplicate pairs within the genome of Caenorhabditis elegans were examined. Most theoretical treatment of evolution by gene duplication assumes that newly duplicated genes are structurally identical and functionally redundant to the ancestral copy. Contrary to this assumption, more than half of newborn gene duplicates analyzed exhibited structural heterogeneity in addition to their region of homology. Duplicated genes tend to be shorter than average, suggesting the frequent occurrence of partial gene duplications. Most newborn gene duplicates reside adjacent to the ancestral copy but in inverse orientation. However, the long-term survival of a duplicated gene is enhanced the further it is located from the ancestral copy. Further analysis of a subset of structurally heterogeneous gene-duplicate pairs utilized the C. briggsae genome to identify the ancestral copy in C. elegans and determine the type of duplication event leading to the origin of a novel gene. Partial gene duplications, often in conjunction with recruitment of new neighborhood sequence exceed the formation of chimeric duplicates. For chimeric duplicates, the genomic sources of unique exons are diverse. These results suggest that altered evolutionary trajectories for duplicates may well be established at the very onset.;In another study, I explore the role of compensatory mutations in the evolution of reproductive incompatibility. The maintenance of populations at small sizes can lead to the accumulation of deleterious mutations. Conditionally beneficial mutations at other loci can interact with the deleterious allele(s) and compensate for their negative effects, thus forming unique gene complexes within a specific genetic background. Multiple lines independently subjected through successive regimes of bottlenecks and expansion were crossed to determine if hybrids exhibit a fitness decline, presumably due to the disruption of these coadapted gene complexes. I discuss my conclusions in reference to a highly contested genetic model of speciation. |
