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'ScienceIQ.com'

Resistance is NOT Futile!
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ScienceIQ.com: Medicine / Germs, Viruses, Microbes
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Maybe if you are a Star Trek heroine up against the Borg, 'resistance is futile.' But if you are a germ that makes people sick, resistance - to antibiotics - is not futile at all.

When penicillin began to be widely used over fifty years ago, it could kill most of the bacteria that made us sick. Such bacteria are called 'pathogens,' to distinguish them from the many bacteria that are harmless or even useful. Nowadays, many pathogens are 'resistant' to a lot of the antibiotics we use to combat them. They have evolved the ability to fight off the effects of the drugs, so the drugs cannot cure you. This can be very dangerous in hospitals, where drug-resistant pathogens can spread rapidly and kill many people.

How can bacteria evolve drug resistance so quickly? The genes for drug resistance are usually not carried as part of the regular chromosome, but on extra rings of DNA called plasmids. These can be passed on to the bacterial cell's descendants, and can also sometimes be passed around to any other bacteria that happen to be in the area, even those of other species. If a drug kills all the susceptible bacteria, any few that are resistant will be free to multiply without competition and take over the population. So we are involved in an 'arms race' between biologists and chemists inventing new antibiotics, and pathogens inventing new ways to resist them.

Fact Credit: Sandy Becker
Image Caption: Antibiotic resistance results from gene action. Bacteria acquire genes conferring resistance in any of three ways.

Image Credit: Image Courtesy U.S. Food and Drug Administration

Further reading
''The Antibiotic Paradox: How the Misuse of Antibiotics Destroys Their Curative Powers
by Stuart B., MD Levy, M.D., Stuart B. Levy
On the web:
* The Rise of Antibiotic-Resistant Infections
by U.S. Food and Drug Administration

* When The Bugs Outsmart the Drugs
by University of Pittsburgh

Here is your science
fact of the day for:
Tuesday October 14, 2003
'ScienceIQ.com'

How Does The Turtle Get Its Shell?
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ScienceIQ.com: Biology / Animals
'' Many invertebrates, such as beetles and lobsters, have shells, but the turtle is the only living vertebrate with a shell (except for the armadillo or course). A turtle's top shell is called the 'carapace', and the matching bottom shell is called the 'plastron.' How does a turtle get his pair of protective shells? Why he grows them of course!

While still inside the egg, a turtle embryo begins to look different from other vertebrates. Instead of curving around to form the familiar rib cage, the turtle embryo's ribs grow straight out from its backbone to form the oval framework of the carapace. The rest of the carapace is formed from calcified tissue deep in the skin of the back. This hardened layer is called dermal bone, and it grows around and fuses to the framework of ribs.

The lower shell, or plastron, is also made of calcified dermal tissue. The front part of the plastron, under the neck, is formed from the shoulder bones, called clavicles (these are dermal too). The rest of the plastron is made of dermal bone. The picture shows that even before it hatches, a baby turtle has begun to form its shell. When it hatches it will look just like an adult turtle, shell and all, only smaller.

Fact Credit: Sandy Becker
Image Caption: Snapping turtle embryo, stained to show the bones. Ribs can be seen spreading out to form the carapace.

Image Credit: Image Credit: Dr. A.C. Burke, Biology Dept., Wesleyan University

Further reading
''Turtles and Tortoises
by Vincenzo Ferri, Anna Bennett (Translator)
On the web:
* Sea Turtles
by ScienceMaster.com

* Turtle and Tortoise Photo Gallery
by Silver City

Here is your science
fact of the day for:
Monday December 9, 2002
'ScienceIQ.com'

Why Can't We Really Clone Dinosaurs?
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ScienceIQ.com: Biology / Reptiles
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You might think, if you saw the movie Jurassic Park, or read the book, that a real live cloned dinosaur would be on the TV evening news any day now. Not very likely! In the fictional version, the dinosaur DNA is resurrected from the stomachs of prehistoric mosquitoes that had sucked some dinosaur blood just before being trapped and preserved in amber 80 million years ago. (Indeed, amber is a wonderful preservative, and just might preserve some DNA!) Then the DNA was transferred into crocodile eggs whose own DNA had been removed. Voila! Baby dinosaurs.

But to clone an animal, as Dolly the sheep was cloned a few years ago, you need not just DNA but whole nuclei - plus an unfertilized egg with its own nucleus removed, to transfer it into. That's why scientists call the cloning process 'nuclear transplantation.' The DNA in sheep or dinosaurs, or people or frogs or mice, or any other animal large enough to see, comes packaged in the nucleus with a lot of associated scaffolding and regulatory proteins to help it carry out the business of running a cell. Naked DNA can't do much by itself. And whole dinosaur nuclei aren't going to be found any time soon.

Some people who have given up on the possibility of cloning dinosaurs think mammoths would be a better bet. Several have been frozen (not fossilized) in the Arctic permafrost in Siberia, and they are only thousands of years old, not millions. Still, the chances of recovering intact nuclei from them is pretty slim. So don't be planning your trip to Jurassic Park, or Mammoth Park, this year.

Fact Credit: Sandy Becker

Further reading
''Baa!: The Most Interesting Book You'll Ever Read About Genes and Cloning (Mysterious You)
by Cynthia Pratt Nicolson, Rose Cowles (Illustrator)
On the web:
* Dinosaurs From Amber?
by Garry Platt

* Cloning and Stem Cells
by New Scientist.com

Marmaduke and the Taco Bell Chihuahua Are Cousins
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ScienceIQ.com: Biology / Animals
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AlthoughYou would never think Marmaduke, the enormous great dane of the newspaper cartoons, and the tiny Taco Bell chihuahua are close relatives. But the fact is, ALL dogs are pretty close relatives. Scientists now believe that all dogs, including the semi-wild dingoes of Australia, Arctic huskies, Shetland sheepdogs, great danes and tiny chihuahuas, are descended from only two original domestic dogs. DNA evidence also suggests that dogs are all derived from wolves, not coyotes or jackals.

The DNA evidence further suggests that dogs were first domesticated about 100,000 years ago. However, the first dog fossils, found in Europe and Asia, date from only 14,000 years ago. The scientists who did the DNA study think that early dogs looked so much like wolves that they can't be distinguished from them in the fossil record until about 14,000 years ago. People later took their dogs with them as they spread out over the globe, to Australia, the New World, and the Pacific Islands. Wild dogs recently discovered in the southeastern United States may be descended from the dogs kept by the Native Americans.

Domestic dogs are smaller than their wild forebears, with smaller brains, less acute senses, and smaller teeth. In appearance and behavior, they are immature, puppy-like wolves.

Fact Credit: Sandy Becker
Image Caption: Although many breeds of dogs exist, they are more similar than not.

Further reading
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How Dogs Came from Wolves: And Other Explorations of Science in Action: Scientists Probe 12 Animal Mysteries
by Jack Myers, John Rice (Illustrator)
On the web:
* Wild Wolves
by Nova

* Domestic Dogs
by Tongham Dog Training Club

Here is your science
fact of the day for:
Monday February 24, 2003
'ScienceIQ.com'

Why Do We Call It A 'Vaccination?'
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ScienceIQ.com: Medicine / Vaccines
'' Smallpox 'vaccinations' are in the news nowadays. What is smallpox and what is a vaccination? Smallpox is one of the oldest and most horrible diseases afflicting the human family. In the past, it killed twenty to sixty percent of victims, and left the survivors with disfiguring scars from the rash.

Early on people realized that survivors of smallpox were immune to further attacks. Over a hundred years before our present form of vaccination, a practice called 'variolation' was used, beginning in China and Asia and reaching Europe by the beginning of the 18th century. Variolation consisted of applying the pus or ground scabs from a patient who had a mild case of smallpox (also called variola, hence the name) to a scratch in the skin. This system wasn't very good: two or three percent of variolated people died of smallpox. But it was better than the 20-60 percent who might die in an epidemic. By the 18th century, people had noticed that those who had had a milder disease called cowpox were also immune from smallpox. Milkmaids often caught it from their cows.

So in the late 18th century, Edward Jenner invented the practice we now know as vaccination, so called from 'vaca', the latin word for 'cow'. Patients were innoculated with material from cowpox lesions, which is much safer than variolation because cowpox is a milder illness. Today, most adults over the age of 35 have a small round scar on their upper arm where they were vaccinated as children.

Fact Credit: Sandy Becker
Image Caption: Smallpox scratch

Image Credit: Image Courtesy of National Institute of Health