THE juicy steak on your plate could soon be traced back to the cow it came
from thanks to its unique 鈥渄igital DNA signature鈥�.
Unlike electronic tags and animal 鈥減assports鈥�, these signatures would be
impossible to fake. They would also stop an animal鈥檚 identity being lost after
it is butchered.
Officials could use the signatures to track animals around the world during
disease outbreaks. The system could also help breeders avoid bad crosses.
Advertisement
Ruedi Fries and his colleagues at the Technical University in Munich are
basing the signature on natural differences in single bases in DNA called single
nucleotide polymorphisms, or SNPs. The genomes of animals such as cows contain
millions of SNPs, combinations of which are unique to a particular individual or
breed.
Fries and his team want to choose between 40 and 96 of these key SNPs. Pick
the right ones and you can create a signature that reveals the identity of a
cow, its relationship to other animals in the herd and its breed. The aim is to
produce a standardised signature that can be used all over the world.
Once Fries and his team have established which SNPs are the best to use, they
will start developing the digital signatures. To do this, they will look for the
presence or absence of a given DNA base at a particular SNP site, and
accordingly assign it either a one or a zero. In this way, they can build up a
unique signature for each cow.
The scheme will have to be cheap enough to set up a large database of
signatures. This will allow researchers to verify the parentage of a
BSE-infected cow, or food hygiene inspectors to clamp down on black-market
goods. Fries believes the signatures can be created with off-the-shelf
technology. 鈥淚f it鈥檚 possible to reduce the costs, it will be done.鈥�
He and his team are in the process of setting up an SNP database to collect
data from livestock geneticists. They hope to finish the evaluation of the SNP
sites within a year. Similar schemes could be set up for other animals such as
sheep or pigs.
Existing methods for tracing farm animals, such as Britain鈥檚 cattle passport
scheme and electronic tagging, are pretty good at identifying animals and their
relationships, says Chris Bostock, director of the Institute for Animal Health
near Oxford. But it would be nice to have 鈥渋ndependent and unchangeable
evidence鈥� to back it up, he says. However, such signatures could only replace
passports and electronic tags if they were very cheap and possible to obtain on
the spot, he adds.
It鈥檚 not just farmers and food scientists who could benefit from the system,
says Fries. Horse breeders could design signatures that act as markers for
inherited diseases such as severe combined immunodeficiency, which can afflict
Arab breeds. They could then avoid breeding carriers with each other鈥攖he
offspring of such unions have a 25 per cent chance of getting the disease.
Although conventional DNA fingerprinting is already being used to confirm an
animal鈥檚 identity and parentage, Fries says that his method has several
advantages. For example, SNPs change less from generation to generation than
fingerprinting markers, making it easier to trace an animal鈥檚 ancestry.