Monthly Archives: March 2014

Sometimes the Tail Wags the Dogma

dna

The word “dogma” has been defined as “a belief or set of beliefs that is accepted by the members of a group without being questioned or doubted.” This word is usually reserved for religious doctrine but is also used in the area of biology.

The so called “central dogma” refers to the idea that the DNA of an organism carries information that is responsible for the traits of that individual. Furthermore, that information flows only in one direction – from the DNA to the body and not from the body to the DNA.

The significance of the central dogma is that the experience an animal has does not change the DNA that he will pass on to his offspring. The only significant changes to DNA occur when periodic accidents happen as the DNA is copied which causes a mutated gene. This abnormal gene may end up helping the mutant offspring survive better than the “normal” members of the population and the new trait is passed on (a process called natural selection).

For example, giraffes did not end up with long necks because as their ancestors stretched up to eat leaves, their necks lengthened. Rather genetic mutations accidentally caused some animals to have longer necks than others and these longer-necked individuals survived better and passed on their long-neck genes. After millions of years of accumulating changes, viola, we have the giraffe!

A study published in the January issue of the journal Nature Neuroscience seems to poke a hole in this central dogma. (Here is a discussion of the study) The researchers exposed a group of male mice to a distinct odor while simultaneously delivering an electrical shock to them. Very soon, the rodents displayed a stress response to just the smell.

These mice were then bred. Amazingly, this odor-related stress reaction was passed on to their pups, despite the fact that they had never smelled the odor before. In fact, the “grandchildren” of the original mice also inherited the reaction. The central dogma of biology does not seem to allow for this outcome.

This study reminds me of my own experience. As a veterinary student, one of my odd jobs was dog sitting for a dog family that included a couple of interesting breeds; Komondors and Pulis. The Komondor is a large sheep herding breed with a white corded coat. They resemble sheep.

The Puli is a medium sized, sheep herding dog with a black, corded coat. Pulis have a very unique way of herding sheep. If a sheep wonders off from the herd, the Puli jumps on its back and rides it around until the sheep gets tired. Then the dog drives it back to the herd.

The thing that intrigued me was that commonly the Pulis I cared for would jump on the backs of the Komondors and ride them around the yard. These Pulis had not been trained to herd and had never even seen another Puli exhibit this behavior. They were apparently born with this strange behavior programmed into their DNA.

Given the central dogma, how could the trained behavior of an animal (mouse or dog) get passed down to future generations? Perhaps there is more to life than DNA and the proteins it codes for. Maybe the word and concept of “dogma” has no place in any science, especially biology – the study of life. Possibly there is more to learn if we loosen our rigid beliefs and open our minds to all the possibilities.

Have you experienced inexplicable animal behavior?