Genomic organizationgenomic organization of prokaryotes, genomic organization in eukaryotes
The hereditary material ie DNAdeoxyribonuclic acid of an organism is composed of an array of arrangement of four nucleotides in a specific pattern These nucleotides present an inherent information as a function of their order The genome of all organisms except some viruses and prions is composed of one to multiple number of these DNA molecules To draw an analogy it can be said that genome when seen from viewpoint of sequences of these nucleotides alone, is like a book which doesn't have any chapters or paragraphs or even sentences Hence, these nucleotides conceal a layer of unapparent information Genomic organisation of an organism is this background layer of information which unassumingly provides multiple layer of information to structure genome from the array of nucleotide sequences
Organisms have a vast array of ways in which their respective genomes are organized A comparison of the genomic organization of six major model organisms shows size expansion with the increase of complexity of the organism There is a more than 300-fold difference between the genome sizes of yeast and mammals, but only a modest 4- to 5-fold increase in overall gene number see the figure on the right However, the ratio of coding to noncoding and repetitive sequences is indicative of the complexity of the genome: The largely "open" genomes of unicellular fungi have relatively little noncoding DNA compared with the highly heterochromatic genomes of multicellular organisms
In particular, mammals have accumulated considerable repetitive elements and noncoding regions, which account for the majority of their DNA sequences 52% non-coding and 44% repetitive DNA Only 12% of the mammalian genome thus encodes for protein function This massive expansion of repetitive and noncoding sequences in multicellular organisms is most likely due to the incorporation of invasive elements, such as DNA transposons, retrotransposons, and other repetitive elements The expansion of repetitive elements such as Alu sequences has even infiltrated the transcriptional units of the mammalian genome This results in transcription units that are frequently much larger 30-200 kb, commonly containing multiple promoters and DNA repeats within untranslated introns
The vast expansion of the genome with noncoding and repetitive DNA in higher eukaryotes implies more extensive epigenetic silencing mechanisms Studies of the genomic organization is thought to be the future of genomic medicine, which will provide the opportunity for personalized prognoses in clinics
- Genome Comparison
- Genome project
- List of sequenced eukaryotic genomes
- Molecular evolution
- ^ Venter G, et al, The Sequence of the Human Genome Science 2001 291 pp1304-51
- ^ R A Harris et al, Human-Specific Changes of Genome Structure Detected by Genomic Triangulation Science 2007 3165822, pp 235-7
- ^ Haig H Kazazian, Jr Mobile Elements: Drivers of Genome Evolution Science, Mar 2004; 303: 1626-32
- ^ West M, et al, Embracing the complexity of genomic data for personalized medicine Genome Res 200616:559-66
genomic organization, genomic organization in eukaryotes, genomic organization in prokaryotes, genomic organization of bacterial, genomic organization of bacterial cell, genomic organization of prokaryotes, genomic organizations
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