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Only 8.2 percent of Human Genome functional: Oxford University researchers

The Oxford University researchers in their study found that only 8.2 percent of the human genome are presently functional or doing something important..

Jul 26, 2014 17:47 IST
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The researchers from Oxford University in their study found that only 8.2 percent of the human genome are presently functional or doing something important.

The study was authored by Chris M. Rands, Stephen Meader, Chris P. Ponting and Gerton Lunter and was published in journal PLOS Genetics on 24 July 2014. The study was funded by the UK Medical Research Council and the Wellcome Trust.

Findings of the Study

  • There is an abundance of genome sequences with short lived lineage-specific functionality
  • Most of the sequence involved in the functional “turnover” is non-coding genome sequence because as species become more closely paired, the mutually constrained genome sequence increases within non-coding sequences.
  • Half of present day non-coding constrained sequence has been gained or lost in approximately the last 130 million years
  • Constrained DNase 1 hypersensitivity sites, promoters and untranslated regions have been more evolutionarily stable than long non-coding RNA loci which have turned over especially rapidly.
  • Much of the short-lived constrained sequences are not detected by models optimized for wider pan-mammalian conservation.
  • Protein coding sequence has been highly stable, with an estimated half-life of over a billion years
  • 8.2 percent (7.1–9.2 percent) of the human genome is presently subject to negative selection and thus is likely to be functional, while only 2.2 percent has maintained constraint in both human and mouse since these species diverged.
  • These results reveal that the evolutionary history of the human genome has been highly dynamic, particularly for its non-coding yet biologically functional fraction.

Purpose of the Study

The study was conducted to clearly identify what percentage of human genome sequence is functional or is of some use since the complete human DNA sequence was mapped ten years ago. Although Encyclopedia of DNA Elements (ENCODE) project in 2012 had identified 80 percent of human genome to be functional but it was mired in controversy.

It was argued that the biochemical definition of function was too broad. This was just because an activity on DNA occurs; it does not necessarily have a consequence. For functionality, one needs to demonstrate that an activity matters.

Nearly 99% of the human genome does not encode proteins, and while there recently has been extensive biochemical annotation of the remaining non-coding fraction, it remains unclear whether or not the bulk of these DNA sequences have important functional roles.

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