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The split gene theory is a theory of the origin of introns, long non-coding sequences in eukaryotic genes between the exons. [1] [2] [3] The theory holds that the randomness of primordial DNA sequences would only permit small (< 600bp) open reading frames (ORFs), and that important intron structures and regulatory sequences are derived from stop codons.
As the split structure of genes is central to eukaryotic biology, their origin has been a major question in biology. Senapathy proposed the "split gene theory," which states that the split structure arose due to the origin of split genes from random DNA sequences, and provided tangible evidence from genome sequences of several organisms.
More recent studies of entire eukaryotic genomes have now shown that the lengths and density (introns/gene) of introns varies considerably between related species. For example, while the human genome contains an average of 8.4 introns/gene (139,418 in the genome), the unicellular fungus Encephalitozoon cuniculi contains only 0.0075 introns/gene ...
[12] [13] The sequence of the 16S ribosomal RNA gene, a vital gene encoding a part of the ribosome, was used to find the broad phylogenetic relationships between all extant life. The analysis by Carl Woese resulted in the three-domain system , arguing for two major splits in the early evolution of life.
Eukaryotic origins of replication control the formation of several protein complexes that lead to the assembly of two bidirectional DNA replication forks. These events are initiated by the formation of the pre-replication complex (pre-RC) at the origins of replication. This process takes place in the G 1 stage of the cell cycle. The pre-RC ...
The tree of life. Two domains of life are Bacteria (top branches) and Archaea (bottom branches, including eukaryotes). The two-domain system is a biological classification by which all organisms in the tree of life are classified into two domains, Bacteria and Archaea.
Nos. 12-3176, 12-3644 IN THE UNITED STATES COURT OF APPEALS FOR THE SECOND CIRCUIT CHRISTOPHER HEDGES, et al., Plaintiffs-Appellees, v. BARACK OBAMA, individually and as
The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.