Junk DNA not junk, says expert

2011-03-10 14:35


Cape Town - The term junk DNA is outdated and was probably given out of naivety, a professor has said.

"The more we study it [non-coding DNA] the more we see signals that it has a functional role in either determining the shape or charge of the helix," Professor Raj Ramesar, director of the Medical Research Council's human genetics research unit, told News24.

The term junk DNA was coined by Susumu Ohno in 1972 and referred to sections of the genome that appeared to have no coding function and a large percentage of the genome is made of this kind of DNA.

The human genome is a long chain of DNA that determines everything about what a person inherits from his or her parents. It is stored on 23 pairs of chromosomes which occupies about three billion DNA base pairs.

"We were incredibly naïve and we're learning new things about it [non-coding DNA]; in fact, we don't even call it junk DNA anymore," said Ramesar on the sidelines of the Joint International Conference of African and Southern African Societies of Human Genetics at the Cape Town International Convention Centre on Wednesday.


About 97% of the function of genes is unknown despite a ten-year project to map the entire genome in the Human Genome Project which was compared to putting a man on the moon, because of its complexity.

Scientists have also mapped the entire genome of Archbishop Emeritus Desmond Tutu in an effort to learn more about the DNA of Africans.

"The project involves the sequencing of named Africans to have their entire genome sequenced. With Desmond Tutu, we know his entire code - it's very unique," said Dr Vanessa Hayes of the J Craig Venter Institute in the US.

"Although it's been 10 years since the completion of the Human Genome Project, not much is known about the DNA of African people," she added.

Non-coding DNA may play a more vital role than what scientists have realised in the past.

"There are small RNA molecules (single-stranded simple form of DNA) that switch things on and off. As we learn more functions, we need to figure out what role they play," said Ramesar.

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