The great leap forward

Similarly, the theory of genome duplication, which was first seriously developed in 1970 by the Japaneseborn geneticist Susumu Ohno (1970), also cannot properly explain the great phenotypic changes that have occurred during the 75 million years since the human and mouse lineages split. Duplications, either of chromosomal regions or of whole genomes, occur naturally, for example, through errors in chromosomal recombination during reproduction. Historically, genome duplication was thought to be a mechanism of evolutionary change because it creates redundant copies of protein-encoding genes with impunity; these copies can have mutations, but the cell will continue to function as it retains an original version of the gene that was duplicated. usually, mutations are deleterious, but the duplicated genes are not generally expressed and so do no harm with no selective pressure acting against them. Occasionally, however, a mutation can result in a potentially useful modification of the gene, which can then be activated and selected. this, it is argued, could create relatively rapidly new functions for genes and thus explain major leaps in evolution. Major gene duplication events certainly occur frequently in plants and microorganisms. a famous example is the complete duplication of the yeast genome, which is thought to have occurred more than 100 million years ago (rikke et al, 2003), after which the two parts evolved independently. consequently, gene or genome duplication could create the evolutionary templates for more sophisticated developments in multicellular eukaryotes. indeed, genomewide comparisons of duplications between humans and chimpanzees indicate that these might have had an important role in the evolution of higher primates that eventually led One of the great challenges in molecular and evolutionary biology is to explain the link between giant evolutionary leaps, such as the colonization of land by plants or the emergence of vertebrates, and the underlying genetic and genomic changes. For a long time, biologists thought that such profound changes in phenotype would be accompanied—if not driven by—equally dramatic upheavals at the genetic level. Similarly, the emergence of the flowering plants within the plant kingdom, or mammalian vertebrates, must surely have been marked by recognizable changes in the genome. yet in fact, it turns out that the genomic changes that enabled these evolutionary developments were far more subtle—it is the regulation, rather than the modification or creation, of genes that has driven macroscopic events throughout evolution.