Fish and chips may hold human DNA clues

The classic fish and chips dish may hold the key to understanding the origins of DNA memory which is critical to human development, a new study suggests.
DNA memory is used to tell a cell what its job is and makes sure it stays dedicated to it.
The unusual looking elephant shark (Callorhinchus milii), commonly used in fish and chips, is only a very distant relative of humans.
Our ancestors split off from elephant sharks more than 460 million years ago.
Now, scientists at the University of Otago in New Zealand have discovered it has a remarkably similar DNA memory system to our own.

"This memory is made up of tiny chemical tags called methylation, which are used to tell a cell what its job is and make sure it stays dedicated to it," said Tim Hore, of the Department of Anatomy at Otago, who led the research.

The DNA memory system that belongs to humans has only been found in vertebrates - animals with a backbone such as mammals, amphibians and fish.
Researchers have long wondered how it evolved and how far back in evolutionary time it exists.
"The fact elephant sharks also use methylation - tagging to turn off genes tells us this memory system has been around a long time," said Julian Peat of the Anatomy Department at Otago.

"Our study identifies elephant shark as the most evolutionarily distant animal that shares this DNA-regulation system with us humans, which makes it very interesting to take a closer look at," Peat said.
Hore said with access to this unique genetic resource, the team is excited about further research on the elephant shark and its DNA.
"The elephant shark is something of a living fossil - it is the slowest evolving vertebrate we know of. It only lives in the cooler waters of Australia and New Zealand, so we are really fortunate to have something this valuable to science in our backyard," said Hore.

"So many things remain mysterious about the elephant shark - we do not know whether this methylation memory persists across generations, or if it contributes to how gender is decided," Hore added.
The study was published in the journal F1000.