Theme: Genomes & Junk DNA

Junk in Your Genome

Transposable Elements: (44% junk)

      DNA transposons:
         active (functional): <0.1%
         defective (nonfunctional): 3%
      retrotransposons:
         active (functional): <0.1%
         defective transposons
            (full-length, nonfunctional): 8%
            L1 LINES (fragments, nonfunctional): 16%
            other LINES: 4%
            SINES (small pseudogene fragments): 13%
            co-opted transposons/fragments: <0.1% ^a

^aCo-opted transposons and transposon fragments are those that have secondarily acquired a new function.

Viruses (9% junk)

      DNA viruses
         active (functional): <0.1%
         defective DNA viruses: ~1%
      RNA viruses
         active (functional): <0.1%
         defective (nonfunctional): 8%
         co-opted RNA viruses: <0.1% ^b

^bCo-opted RNA viruses are defective integrated virus genomes that have secondarily acquired a new function.

Pseudogenes (1.2% junk)
      (from protein-encoding genes): 1.2% junk
      co-opted pseudogenes: <0.1% ^c

^cCo-opted pseudogenes are formerly defective pseudogenes those that have secondarily acquired a new function.

Ribosomal RNA genes:
      essential 0.22%
      junk 0.19%

Other RNA encoding genes
      tRNA genes: <0.1% (essential)
      known small RNA genes: <0.1% (essential)
      putative regulatory RNAs: ~2% (essential) Protein-encoding genes: (9.6% junk)
      transcribed region:  
            essential 1.8%  
            intron junk (not included above) 9.6% ^d

^dIntrons sequences account for about 30% of the genome. Most of these sequences qualify as junk but they are littered with defective transposable elements that are already included in the calculation of junk DNA.

Regulatory sequences:
      essential 0.6%

Origins of DNA replication
      <0.1% (essential) Scaffold attachment regions (SARS)
      <0.1% (essential) Highly Repetitive DNA (1% junk)
      α-satellite DNA (centromeres)
            essential 2.0%
            non-essential 1.0%%
      telomeres
            essential (less than 1000 kb, insignificant)

Intergenic DNA (not included above)
      conserved 2% (essential)
      non-conserved 26.3% (unknown but probably junk)

Total Essential/Functional (so far) = 8.7%
Total Junk (so far) = 65%
Unknown (probably mostly junk) = 26.3%

For references and further information click on the "Genomes & Junk DNA" link in the box

LAST UPDATE: May 10, 2011 (fixed totals, and ribosomal RNA calculations)

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November 11, 2006
Sea Urchin Genome Sequenced

The sea urchin genome is 814,000 kb or about 1/4 the size of a typical mammalian genome. Like mammalian genomes, the sea urchin genome contains a lot of junk DNA, especially repetitive DNA. The preliminary count of the number of genes is 23,300. This is about the same number that we have in our genomes. Only about 10,000 of these genes have been annotated by the sea urchin sequencing team.

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