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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.
The domino theory suggests that if one gene of a cellular process becomes inactivated, then selection in other genes involved relaxes, leading to gene loss. [51] When comparing Buchnera aphidicola and Escherichia coli , it was found that positive epistasis furthers gene loss while negative epistasis hinders it.
Periannan Senapathy is a molecular biologist, geneticist, author and entrepreneur.He is the founder, president and chief scientific officer at Genome International Corporation, a biotechnology, bioinformatics, and information technology firm based in Madison, Wisconsin, which develops computational genomics applications of next-generation DNA sequencing (NGS) and clinical decision support ...
This page was last edited on 16 January 2024, at 14:18 (UTC).; Text is available under the
Another theory is that the spliceosome and the intron-exon structure of genes is a relic of the RNA world (the introns-first hypothesis). [47] There is still considerable debate about the extent to which of these hypotheses is most correct but the popular consensus at the moment is that following the formation of the first eukaryotic cell ...
Phylogenetic trees also have trouble depicting microevolutionary events, for example the geographical distribution of muskrat or fish populations of a given species among river networks, because there is no species boundary to prevent gene flow between populations. Therefore, a more general phylogenetic network better depicts these situations.
Crossing two members of the F1 generation produces the second filial (F2) generation. Probability theory predicts that three quarters of the F2 generation will have the dominant allele's phenotype. And the remaining quarter of the F2s will have the recessive allele's phenotype. This predicted 3:1 phenotypic ratio assumes Mendelian inheritance.
One example is a gene drive complex, called a segregation distorter, that "cheats" during meiosis or gametogenesis and thus is present in more than half of the functional gametes. The most studied examples are sd in Drosophila melanogaster ( fruit fly ), [ 9 ] t haplotype in Mus musculus ( mouse ) and sk in Neurospora spp. ( fungus ).