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Real cashmere?

“One hundred percent cashmere” – is it true or just persuasive advertising? A DNA analysis of the wool can reveal whether the pullover is really made from the fine, soft underwool of the cashmere goat, or if ordinary sheep’s wool has been substituted for this costly fiber.

It says “one hundred percent cashmere” on the label, but is this really the case? Or is it dishonest advertising intended to hide the fact that the valuable underwool of the cashmere goat has been adulterated with ordinary sheep’s wool? Researchers at the Fraunhofer Institute for Molecular Biology and Applied Ecology IME in Schmallenberg are now in a position to be able to unmask such fraudulent claims. “To do this, we have to extract the DNA from the wool,” says Dr. Björn Seidel, manager of the project at the IME. This is a difficult undertaking, as hair only contains minute traces of DNA. Moreover, wool often undergoes chemical treatment and is heated during the dyeing process, which also destroys a great deal of the genetic material that is present. “We therefore have to replicate the DNA that we extract from the wool a million times over before we are able to analyze its origins and state definitively whether it comes from a goat, a sheep or a camel for instance,” explains Seidel. The replication of the DNA is carried out with the help of a technique commonly used in molecular biology, known as polymerase chain reaction or PCR for short. The double strand of DNA is heated, causing it to divide into two separate strands. Researchers simultaneously add small DNA fragments, or ‘primers,’ that attach themselves to the corresponding segment of wool DNA, analogous to a key fitting into a lock. This fragment then acts as a kind of ‘anchor’ to which the individual building blocks of DNA in the surrounding solution attach themselves, completing the puzzle and forming two new double strands of the genetic material. This step is repeated many times over, resulting in a million-fold replication of the DNA, so that even the very small quantities present in hair can then be detected. Normally primers that replicate either goat’s or sheep’s DNA are added during this technique. But as Seidel points out, “this means that you only find what you are looking for. With our method, we can simultaneously replicate the DNA of all types of wool present in the sample using only one primer. Our process is therefore much quicker than existing PCR techniques.” The researchers then add an enzyme that splits the DNA at very specific points. By analyzing the length of the resulting strands, it is possible to identify from which animal the DNA and therefore also the wool originated. The researchers are now working on the next step, which is to be able to determine the proportions of the different types of wool in a particular sample.

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