DNA Day experts answer your questions about junk DNA

20 April 2012

Above: Image © RKaulitzki, iStockphoto.com

Got junk (DNA)? What is it?

I think you are referring to "non coding" DNA? The function of non coding DNA is still poorly understood, but we do know that some plays a role in important biological functions such as assisting in transcriptional and translational regulation of the protein coding sequences

- Answer provided by Dr. Monique Haakensen

What is junk DNA?

We have 6 billion bases of DNA, but only 1% of that is made up of genes. So we used to think that all the other DNA was just junk and wouldn't mean much because it didn't code for anything. We know this is not the case because there can be regions upstream of genes that regulate them in different ways. We need this DNA to sometime align the gene to transcription factor.

- Answer provided by Dr. Dennis McCormac

It is proven that a large majority of DNA is actually deemed 'useless' as they do not code for any proteins. If this large protion of DNA is useless, then why do a large majority of organisms contain very similar DNA sequences up to 98% in comparison between humans and chimpanzees. To summarize, why do many organisms contain the similar or the same junk DNA if it has no benefit to the organism and does not code for any specific protein?

You may have heard phrases like "we share 99% of our DNA with chimps" or something similar. While this is true for certain definitions of "share", what is becoming ever more obvious is that what defines the development of higher organisms such as ourselves is not just the genes we have, but all of the complex genetic feedback mechanisms that regulate what genes are expressed where and at what time. Many of these gene regulatory regions are in the "useless" DNA.

- Answer provided by Dr. Paul Gordon

Why is part of our DNA useless?

In the past, scientists believed that only a small part of the DNA has value (usually focused on those areas of the chromosomes that code for proteins and the promoters that regulate protein expression) and the rest had no function. We have now discovered what we thought was 'junk' DNA now has a important biological function. There is some discussion of how much of it has function among scientists working in this area. Many researchers point out that this DNA is regulated at a higher level with what is called epigenetics (epi meaning on or above... DNA). There are enzymes that cause chemical changes in the DNA, the histones (proteins that wind the DNA to compact) that impact expression of RNA, and consequently proteins. There is even some consideration that these DNA chemical modifications (called marks) can be impacted by environmental factors.

- Answer provided by Dr. David Charest


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