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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 Britten–Davidson model, [1] [2] also known as the gene-battery model, [3] is a hypothesis for the regulation of protein synthesis in eukaryotes.Proposed by Roy John Britten and Eric H. Davidson in 1969, the model postulates four classes of DNA sequence: an integrator gene, a producer gene, a receptor site, and a sensor site.
Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion. [1] Gene conversion can be either allelic, meaning that one allele of the same gene replaces another allele, or ectopic, meaning that one paralogous DNA sequence converts another.
"The structure of a eukaryotic protein-coding gene. Regulatory sequence controls when and where expression occurs for the protein coding region (red). Promoter and enhancer regions (yellow) regulate the transcription of the gene into a pre-mRNA which is modified to add a 5' cap and poly-A tail (grey) and remove introns.
Gene structure is the organisation of specialised sequence elements within a gene. Genes contain most of the information necessary for living cells to survive and reproduce. [ 1 ] [ 2 ] In most organisms, genes are made of DNA, where the particular DNA sequence determines the function of the gene.
Multivariate statistical analysis of codon use within genomes with unequal quantities of coding sequences on the two strands has shown that codon use in the third position depends on the strand on which the gene is located. This seems likely to be the result of Szybalski's and Chargaff's rules.
The G-value paradox arises from the lack of correlation between the number of protein-coding genes among eukaryotes and their relative biological complexity. The microscopic nematode Caenorhabditis elegans, for example, is composed of only a thousand cells but has about the same number of genes as a human.
Figure 1. TATA box structural elements. The TATA box consensus sequence is TATAWAW, where W is either A or T. In molecular biology, the TATA box (also called the Goldberg–Hogness box) [1] is a sequence of DNA found in the core promoter region of genes in archaea and eukaryotes. [2]