Modern Biology
Muscle Disease Gene Identified in Fish
Bird Flu Mutation Risk
Platelets Help Tackle Bacteria
Untangling The Model Muddle
Cloning - The Good, The Bad and The Ugly
Unpacking the Human Genome Project
Does a Hot Mint Still Taste Cold?
Do Bald Men get all the Girls?
Why Plants Make Caffeine
Turning your Brain into Blood - How Stem Cells Work
The Microchimera Mixture
Forgetful Flies - A tale of two halves (of the brain)
The Smelly World of Mice and Men!
How animals develop from an embryo
Ricin : The Secret Assassin
Why drink Wine ?
Genetically Modified (GM) Plants
Big Fish, Little Sea
Something in the Air
What's On The Menu ?
What is the purpose of sexual reproduction?
Therapeutic Cloning, and Stem Cell Research
What is Living in my Mouth?
Genes for Bigger Brains
  The Smelly World of Mice and Men!
For instance, airborne molecules of acetic acid are responsible for the characteristic smell of vinegar. However, different types of vinegar, such as malt vinegar and wine vinegar smell different because they give off different mixtures of other chemicals. Some odours such as fresh coffee are extremely complex mixtures of hundreds of different odourants. We are able to sense these chemicals because they bind to protein receptors on cells in our nose. These receptors are a bit like locks that can only be opened by certain chemical keys. There are a variety of different receptors in the nose, which respond to different types of chemicals and produce the sensation of different smells.

Each receptor protein is produced from a gene. Our evolutionary ancestors only possessed a few genes for different receptors, and consequently had a limited sense of smell. Over many generations these genes have been duplicated and small random changes have occurred. This has produced families of slightly different receptors, which increase the range of chemicals to which the nose is sensitive. The largest number is found in rodents, such as mice, which possess genes for around 1000 different receptor types. However, changes to the receptor genes can also stop them working. For humans only about 350 genes are thought to produce functional receptors out of the 900 possible receptor genes that have been identified in the human genome.

What does this mean for the abilities of mice and humans to sense smells? The repertoire of human odourant receptors covers as wide a range of chemical types as is covered by the receptors of mice, but not in as much detail. In other words we get a much coarser grained view of the odour world than mice. We're a bit like a colour-blind person having difficulty picking out an orange rucksack against the green background of a field. Humans find that certain chemicals smell similar to each other and may merge into the background, whereas they would stand out a mile to a mouse. Many animals have a greater number of odourant receptors than humans, and therefore a better sense of smell. This is probably why dogs are so much better at tracking scents than we are, although come to think about it, another reason may be that their nose is that much closer to the ground!
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Bigfoot: The Nitrogen Problem
A Traveller's Guide to Bed Bugs
A spider web's strength lies in more than its silk
Thai police bust Bangkok rare wildlife 'butchers'
Castaway lizards provide insight into elusive evolutionary process
Bouquet bargains trade off for life
18 endangered dolphins spotted off Borneo: WWF
Tiny primate 'talks' in ultrasound
Steroids control gas exchange in plants
Fossil cricket reveals Jurassic love song
Rhino dies after anti-poaching treatment in S.Africa
Lions adapt to winter at Canada safari park
Invasive alien predator causes rapid declines of European ladybirds
Not the black sheep of domestic animals
Coaxing a Shy Microbe to Stand Out in a Crowd
How the zebra got its stripes
Fruit flies drawn to the sweet smell of youth
FLORA AND FAUNA Genetic Rosetta Stone unveiled in Nature
Ultraviolet protection molecule in plants yields its secrets
Indian village relocated to protect tigers
Explosive evolution need not follow mass extinctions
Plants use circadian rhythms to prepare for battle with insects
Armenia culls wolves after cold snap attacks
The Developing Genome?
Tempur-Pedic Mattress Comparison
Chromosome analyses of prickly pear cacti reveal southern glacial refugia
Poachers slaughter hundreds of elephants in Cameroon
'Founder effect' observed for first time
A Blue Future For Global Warming
Hitchhikers guide to Science
The Art of The Barbecue
Lost your bottle?
A Crossword a Day keeps the Doctor at Bay
Bio-plastics: Turning Wheat And Potatoes into Plastics
Why Don't Woodpeckers Get Brain Damage?
Protein Origami: Pop-up Books & Nature's Polymers
The Science of Parasites
Synthetic Biology: Making Life from Scratch
Flies are creatures of habit
What is Love?
How do plants develop?
What IQ Tests Can't Tell You
What is the Weirdest Experiment Ever?
Humble Honey Bee Helping National Security
Southern Right Whales
The Ocean's Cleaners
Barnacles "mussel" in
Food Date Coding Decoded
Photorhabdus luminescens: The Angel's Glow
Evolution Through the Looking Glass
I'm a Civet: Get me out of here!
No Smoke Detectors in the Sea