Can Dogs Smell Genes?

Where does the limit of a dog's ability to smell things lie? 

Sniffer dogs are trained to detect odors as diverse as cocaine and explosives. Indeed, some dogs are able to detect cancer in humans, simply by their sense of smell. Then there are the dogs that can detect their diabetic owner's low blood sugar levels and warn them to eat something. 

With these seemingly magical powers, does that mean dogs can smell something as infinitesimally tiny as genes?

Actually, this is a step too far with regards sense of smell. Dogs have amazingly sensitive noses when it comes to detecting odor molecules. All body cells contain genes, but these codes are for the structure of the cell and the function of that part of the body. As such, genes are odorless...unless they code for a function that creates a smell. But even then, the dog detects the smell rather than the gene coding for it. 

You may think that a sniffing dog is just that... a sniffing dog. However, dogs have different ways of scenting the air, depending on how far away or close the odor is, and whether that odor needs to be located or 'read'. 

When a detection dog is asked to follow a particular scent, they start by widely sampling the air so as to work out where the smell is strongest. 

To do this, the dog moves forward rapidly, following a zig-zag path and taking lots of shallow sniffs. By doing this, they find the path where the smell is most intense and follow that. Once they have localized the smell, they then slow down, in order to pinpoint it exactly. 

In the canine world of sniffs, this second sort of scenting enables the dog to read the scent message left by another dog. In the detection world, it is how the dog zeroes in on a concealed substance. To do this, the dog slow right down and takes fewer, but much deeper breaths. 

A detection dog is trained to alert the handler to a find in a specific way. For a explosives detection dog, this might mean barking. Whilst for a cancer alert dog, the dog will be trained to lie down quietly, which alerts the handler but without alarming the patient. 

There are some jaw-dropping statistics that illustrate just how sensitive a dog's sense of smell is. All dogs have a better sense of smell compared to people, because of adaptations of the nose and brain that favor this sense. However, some dog breeds have specialized further, with dogs such as Bloodhounds and Beagles being notorious for their noses. These are examples of scenthounds, or, dogs that were selectively bred together to create dogs that are super-gifted at sniffing. 

Originally, scenthounds were used for hunting and tracking. This enabled man to follow prey in order to make a kill and eat, or to track wild animals for sport. However, in the 20th century, the dog's awesome sense of smell was put to more refined purposes such as detecting explosives. 

It occurred to handlers that the potential to train a dog to sniff out a specific substance was much wider than previously thought. In the modern day, so-called sniffer or detection dogs are trained to detect a wide range of smells from illegal drugs through to people trapped in debris. 

Dogs have superior ability to follow scents because their evolution favored a sense of smell, rather than vision or touch. When compared to a person, a dog's sense of smell is 10,000 to 100,000 times more sensitive than the human nose. In practical terms, this means a dog could detect one rotten apple amongst two million barrels of apples.

Dogs achieve this by having a highly-tuned processing center in the brain and lots of scent receptors in the nose. Indeed, even that trademark wet nose is adapted to capturing smells, as the moist surface traps scent molecules to pass them upwards into the nasal chamber. 

Inside the dog's snout are turbinate bones coated in moist mucosa lined with trillions of scent receptor cells. This is even more clever than it sounds because those turbinate bones are made up of very fine scrolls of bones, which hugely increase the surface area available to receive scent molecules. 

Then, once a receptor has detected a scent, messages are passed to the brain. A dedicated processing center, the olfactory bulb, decodes all those messages and identifies the smells. The olfactory center is again much larger in the dog (around 2% of the total brain capacity) compared to a person (a miserly 0.03% of the brain is dedicated to smell.)

All this adds up to canines having a super-sensitive sense of smell... but still not sensitive enough to detect genes. 

The very nature of genes means that dogs are not able to smell them. However, it's possible to train a dog to track or follow a scent, which is something that many dogs enjoy. 

Start in a room or yard with few distractions. It will help the dog's concentration if they've recently had a walk, to burn off excess energy. 

Now, show the dog a favorite toy, put it on the floor, and praise the dog when they pick it up. Have the dog give you the toy and then reward them with a treat or game of tug. 

Have someone distract the dog whilst you drag the toy across the ground and partially hide the toy behind a bucket. At this stage, don't make it difficult to find. Encourage the dog to find the toy. In a game of "Hot" and "Cold", praise the dog when they're on the right track, but sound disappointed when they take a wrong turn. Then, when the dog sees the toy and gets it, give them lots of praise. 

Keep repeating this, but place the toy in different locations. As the dog gets the hang of things, they'll start to track the toy using their sense of smell as a helping clue. Once the dog's nose is automatically going to the ground, you can start getting more devious about hiding the toy, as the dog will be tracking by scent and not sight.