Junk DNA might be the se­cret to our genome

Wangaratta Chronicle - North East Regional Extra - - News - WITH CHRIS FEBVRE,

YOU are a chim­panzee. Well, you’re al­most a chim­panzee. In fact, your genome is 98.5 per cent iden­ti­cal to that of a chim­panzee’s. This means one of two things. Ei­ther some­one should call the lo­cal wildlife au­thor­i­ties and have you placed in an an­i­mal en­clo­sure, or ge­net­ics is a re­ally weird and baf­fling branch of sci­ence. For­tu­nately for you, it’s the lat­ter. And the more sci­en­tists learn about our genome, the more weird and baf­fling things be­come.

Prior to the hu­man genome be­ing mapped in 2001, it was es­ti­mated that our genome should con­tain in the vicin­ity of one hun­dred thou­sand genes (pro­tein cod­ing DNA), but the teams re­spon­si­ble for the map­ping clocked the to­tal at roughly thirty thou­sand genes.

And now ge­neti­cists have dis­cov­ered that the to­tal is closer to twenty thou­sand.

To put that in per­spec­tive, a mi­cro­scopic worm con­sist­ing of just one thou­sand cells holds a gene count sim­i­lar to our own.

Given the mas­sive dis­par­ity be­tween the com­plex­ity of an or­gan­ism such as our­selves, and that of a mi­cro­scopic worm, it begs the ques­tion as to how such a thing is pos­si­ble.

Fur­ther­more, given that our genome is so close to that of a chimp, why are we so bi­o­log­i­cally dif­fer­ent, not just in our ap­pear­ance, but in our rel­a­tive cog­ni­tive abil­i­ties?

The an­swer may just lie in what Dr Fran­cis Crick, codis­cov­erer of the dou­ble he­lix struc­ture of DNA, la­belled as ‘Junk DNA’ in 1970.

At the time, this junk DNA ap­peared to hold no ap­par­ent pur­pose as it was non- cod­ing (mean­ing that it did not code pro­teins and thus did not hold in­for­ma­tion per­ti­nent to our struc­ture as an or­gan­ism).

But con­sid­er­ing that this junk com­prises roughly 97 per cent of our ge­netic struc­ture, sci­en­tists have long spec­u­lated that, far from be­ing use­less, this junk yard of ran­dom DNA might just hold the key to the ques­tion of why we are hu­man, and why a gi­raffe is a gi­raffe.

This comes as no great sur­prise to evo­lu­tion­ary bi­ol­o­gists, most of who have long main­tained that one hun­dred thou­sand pro­tein cod­ing genes would prove to be so com­plex as to be fa­tal for an or­gan­ism, sim­ply be­cause the chances of off­spring suf­fer­ing ex­ten­sive and life threat­en­ing mu­ta­tions would be ex­ces­sively high.

The jury is out for the time be­ing as there is still much work to be done, but it would seem that ge­neti­cists will be up to their el­bows sift­ing through the DNA equiv­a­lent of a rub­bish dump for the fore­see­able fu­ture.

But as they say, ‘One man’s trash is an­other man’s trea­sure’.

They may be more right than they ever knew.

PRAC­TI­CALLY IDEN­TI­CAL: The hu­man genome is 98.5 per cent iden­ti­cal to that of a chim­panzee’s.

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