ĭuplicated genes are also called paralogs in contrast to orthologs, to refer to their homologous relationship, i.e., the fact that they descend from a common ancestor via a duplication event rather than a speciation event. Recently, the analysis of the evolution of cancer suppression in mammals revealed that species known to be resistant to cancer contain the most cancer gene copies. For example, the analysis of human genes linked to diseases made it possible to show that 80% of them have been duplicated in their evolutionary history, the disease-associated mutation being associated with only one of the duplicated copies. On the other hand, duplication may also have important deleterious effects in humans and can be associated with some diseases. Although less numerous than in plants, some examples also exist in animals such as in Drosophila where the hybrid-male sterility gene Odysseus was formed by gene duplication. In particular, this mechanism is thought to have generated the new flowering plant Mimulus peregrinus within the last 140 years. Gene duplication can also be involved in speciation, especially via whole genome duplication (WGD) as it is suspected in plants, where a correlation has been observed between WGD and increased rates of speciation or divergence. For example, gene duplication has played a role in nutrient transport under stress conditions, in protection against heat, cold, or salty environments, in the resistance to drugs and pesticides, but also in the adaptation to domestication. In particular, numerous examples have described the role of duplication in some cases of adaptation to environmental conditions. Among the different possibilities, gene duplication is a very important mechanism providing new genetic material and opportunities to acquire new functions. Moreover, genomes are highly dynamic with several ongoing processes allowing the creation of genetic novelty necessary for species to evolve and adapt to changing environments. The eukaryotic genome organization is complex and contains different types of sequences with much of them being non-coding sequences that may have an important impact on genome functioning and regulation. Hence, understanding the specificity of the duplicated genes of interest is a great asset for tool selection and should be taken into account when exploring a biological question. Indeed, these bioinformatic approaches differ according to the underlying duplication mechanism. In this review, we first describe the evolutionary processes allowing the formation of duplicated genes but also describe the various bioinformatic approaches that can be used to identify them in genome sequences. Due to their particular importance, the identification of duplicated genes is essential when studying genome evolution but it can still be a challenge due to the various fates duplicated genes can encounter. Various processes are known to allow a gene to be duplicated and different models explain how duplicated genes can be maintained in genomes. How closely matching sets of genes can belong to entirely different species is one of the great mysteries of modern biology.Gene duplication is an important evolutionary mechanism allowing to provide new genetic material and thus opportunities to acquire new gene functions for an organism, with major implications such as speciation events. However, not all differences between species can be explained by gene differences alone. Because of this close similarity, scientists think that it is the sequence of genes, as well as the types of genes themselves, that account for most of the differences between the two species. Just how different are the genes making up different life forms? In the case of the human and the chimp, not much: about 98 percent of the DNA in a chimpanzee cell is identical to the DNA in a human cell. The kinds of proteins, the amounts, and the order in which they are made all help determine how one type of cell differs from another and, ultimately, how one species of organism differs from another. These proteins are used to repair cells and make new ones. Genes contain the chemical information needed to create different kinds of proteins. Each gene is a specific segment of DNA, occupying a fixed place on a chromosome. Did You Know? What makes a human different from a chimpanzee? Much of the answer lies in the genes, the basic units of heredity.
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