Speciation and gene duplication followed by modifications are considered to be the primary events of genome evolution and were well recognized in the pre genomic era. The genes having a relationship of common descent are termed as homologs. The concept of orthology and paralogy were introduced by Walter Fitch in 1970 to distinguish between homologous genes according to their mode of descent. Orthologs are homologous genes related via vertical descent or speciation whereas paralogs are homologous genes originating through duplication in a certain lineage [1]. Paralogs can be further classified into outparalogs and inparalogs depending upon whether the gene duplication antedate or postdate the speciation event respectively [2].
A one-to-one correspondence of orthologs and paralogs can help to reconstruct evolutionary history of genes by comparing the sequences of all genes between genomes from different taxa and with each genome. However combination of speciation and gene duplication entangles orthologs and paralogs into complex web of relationships involving one-to-many and many-to-many correspondence. The emerging field of evolutionary genomics have also highlighted the importance of gene loss, horizontal gene transfer and gene rearrangements in genome evolution which can further complicate the evolutionary relationships of homologous genes [3].
Apart from reconstructing the evolutionary relationships, gene orthology have served the purpose of transfer of functional information from experimentally characterized genes in model organisms to uncharacterized orthologs in newly sequenced genomes. This is necessitated by the infeasibility of experimentally determining the function of all the genes of numerous sequenced genomes. The va...
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...ng RNAseq data and different measures of expression similarities. The pairwise comparisons of expression profiles reveal higher similarity between orthologs than between within-species paralogs and between-species paralogs. This study also validates the presence of background noise in expression data when a correlation coefficient is used as measure of expression similarity. However this study can be considered redundant and simplified as it only validates previous findings of Chen and Zhang using similar approaches on same type of data. This study and the studies of Altenhoff et al. and Chen and Zhang are not final proofs for ortholog conjecture. Gene expression data serves only as a proxy for gene function while GO annotations are incomplete and have biases and errors. Hence further studies using complete functional data is necessary to prove ortholog conjecture.
Alu elements are a class of transposable genes found exclusively in the genomic sequences of primates. Averaging in lengths of approximately 300 base pairs, Alu elements are classified as being short interspersed elements, more commonly referred to by the acronym SINEs. These elements interject themselves into the DNA sequence by means of retroposition. Once established into the genome, Alu elements are considered to be stable, only rarely being subjected to deletion. Initial studies on the prevalence of Alu inserts within the modern human genome was calculated to be nearly 5% (Comas, Plaza, Calafell, Sajantila, & Bertranpetit, 2001), however, more recent research indicates that the actual percentage of various Alu elements account for nearly 11% of the DNA sequence (Deininger, 2011). Alu elements are of great importance to scientists, particularly to those who wish to study evolution, as well as, migrational patterns of early human populations.
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The second of Tinbergen’s questions Phylogeny looks at the evolutionary explanations of development, as opposed to just how behaviour has adapted, including mutations in response to environmental changes. Some of these mutations remain in species even after necessity has gone, and can influence future characteristics of that species. The third of Tinbergen’s questions looks at Causation,...
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Charles Darwin’s theory of natural selection explains the general laws by which any given species transforms into other varieties and species. Darwin extends the application of his theory to the entire hierarchy of classification and states that all forms of life have descended from one incredibly remote ancestor. The process of natural selection entails the divergence of character of specific varieties and the subsequent classification of once-related living forms as distinct entities on one or many levels of classification. The process occurs as a species varies slightly over the course of numerous generations. Through inheritance, natural selection preserves each variation that proves advantageous to that species in its present circumstances of living, which include its interaction with closely related species in the “struggle for existence” (Darwin 62).
Ridley, M. (1999). Genome: The Autobiography of a Species in 23 Chapters. New York: HarperCollins.
The human archaeological record is a long and undefined story that may be the most complex question researched today. One of the big questions in human history is the disappearance of the Neanderthal people from the archaeological record around 30,000 BP. While for thousands of years Neanderthals and Anatomically modern humans crossed paths and perhaps lived in close relations, we have yet to really understand the degree to which they lived together. My hypothesis is that these two hominids, Neanderthals and Anatomically Modern Humans, interbred exchanging genes after Modern Humans dispersed from Africa and creating like cultures and material remains. The differences between Neanderthal and Modern humans are not only physical but also genetically evolved and this research will determine an estimated amount of admixture between the two groups.
Genes are expected to give offspring hereditary similarities to the parent. However, this was not known and Gregory Mendel asked himself what was passed on by parents to their offspring that is the basis for similarity. Mendel would go on through experiments with pea plants to answer short questions. The answers were short as well as to say that the passing of characteristics from parents to the offspring is throug...
M Dufrasne, I. M. (2013). Journal of Animal Science. Animal Genetics , Volume 91 (12).
Without evolution, and the constant ever changing environment, the complexity of living organisms would not be as it is. Evolution is defined as a process that results in heritable changes in a population spread over many generations (8).Scientists believe in the theory of evolution. This belief is based on scientific evidence that corroborates the theory of evolution. In Figure 1 the pictures of the skulls depict the sequence of the evolution of Homo-sapiens. As the figure shows, man has evolved from our common ancestor that is shared by homo-sapiens. The change of diet of homo-sapiens over time has thought to contribute to the change in jaw structure and overall skull shape.