Scientists say rare plant has biggest genome yet

Kate Kelland - When it comes to genomes, size matters -- and British scientists say a rare and striking plant native to Japan is in a perilous position.

Researchers at Britain's Kew Botanical Gardens say the plant, Paris japonica, has the largest genome yet recorded, putting it at high risk of extinction.

"Some people may wonder what the consequences are of such a large genome and whether it really matters if one organism has more DNA than another," said Ilia Leitch, a researcher at Kew's Jodrell Laboratory. "The answer to this is a resounding 'yes'"

"Having a large genome increases the risk of extinction. The larger it is, the more at risk you are."

The vast range of genome size -- the amount of DNA -- in plants and animals has long fascinated and puzzled scientists.

With 152.23 picograms (pg) of DNA, the Paris japonica has around 15 percent more than the previous record holder, the marbled lungfish or Protopterus aethiopicus, with 132.83 pg. It is also more than 50 times bigger than the human genome, which is 3.0 picograms. A picogram is one trillionth of a gram. ...

via Scientists say rare plant has biggest genome yet | Reuters.

If laid end-to-end it would stretch to more than 300 feet.

"We certainly didn't expect to find it," she said.

A genome is the full complement of an organism's DNA, complex molecules that direct the formation and function of all living organisms. The size of an organism's genome is typically measured by the number of bases it contains - base pairs being the building blocks of DNA. The human genome, for example, has about 3 million bases and measures about 6 feet in length.

The marbled lungfish has a whopping 130 million bases. And the 12-inch (30-centimeter) flower studied by Leitch turns out to have 150 million.

Outside experts were impressed.

"This is certainly an enormously large genome," said Nick Lane, a fellow at the Department of Genetics, Evolution and Environment at University College London. "I don't know of any larger genomes among plants or animals."

Still, he cautioned that micro-organisms known as amoebas might have even longer codes, saying that the record "might not last long." ...

via  sunherald.com

One of the largest genomes belongs to a very small creature, Amoeba dubia. This protozoan genome has 670 billion units of DNA, or base pairs. The genome of a cousin, Amoeba proteus, has a mere 290 billion base pairs, making it 100 times larger than the human genome.

via genomenewsnetwork.org