DNA deletion research surprises scientists

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DNA deletion research surprises

scientistshttp://www.iol.co.za/index.php?set_id=1 & click_id=117 & art_id=qw1098

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October 20 2004 at 09:33PM

 

By Patricia Reaney

 

London - It's called the book of life but mice, and perhaps humans,

can still thrive even when chapters are missing, scientists said on

Wednesday.

 

The mouse genome, or genetic blueprint, was published nearly two years

ago. Mice and men share 99 percent of their genes, including so-called junk

DNA which has no known function.

 

Intrigued to find out what junk DNA does, scientists in the United

States removed swathes of junk DNA sequences from mice. To their amazement

it made no difference in the rodents.

 

The finding may have profound implications for researchers

investigating the cause of illnesses because sequences of junk DNA that were

deleted are shared by humans.

 

Being able to discard areas of genome means scientists searching for

the causes of illnesses and cures may now have fewer pages of the book of

life to search.

 

" It was an architectural approach. If you want to question whether a

wall is weight-bearing you remove it and see if the ceiling falls in, " said

Edward Rubin, director of the United States Department of Energy Joint

Genome Institute (JGI).

 

" We removed these big chunks (of DNA sequence) and there was barely

any change, " he said. " It suggests there are large stretches of potentially

disposable DNA in the genome. "

 

By comparing the mouse and human genomes, scientists from JGI and the

Lawrence Berkeley National Laboratory in California and other researchers

hope to improve understanding of what makes us human.

 

Mice have roughly 25 000 genes, a similar amount to humans. Mice and

men share compatible cell and organ systems. The rodents also breed quickly,

so millions of them are used in laboratories around the globe to study how

genes work.

 

Identifying disposable DNA sequences in mice may narrow the search for

disease-causing genes in humans.

 

" By and large, these deletions were tolerated and didn't result in any

noticeable changes, " said Marcelo Nobrega, who collaborated on the research

which is reported in the science journal Nature.

 

" An important caveat, however, is that no matter how detailed our

analyses, our ability to test for a particular characteristic in mice is

limited, " he added in a statement.

 

The scientists compared the genome of the mouse and humans and

identified regions to delete. Using molecular engineering they snipped out

DNA sequences in mice embryonic stem cells and generated a strain of mice

with the abridged genome.

 

They analysed features such as growth, longevity and molecular and

biochemical features between normal mice and those with the abridged genome

but found no difference.

 

" As far as disease goes, these are probably regions where there may be

functions but they are subtle at the best, " said Rubin.