Posted on 12/21/2004 8:45:42 AM PST by PatrickHenry
The wide range of variety in domesticated dogs from the petite Chihuahua to the monstrous mastiff has powered a new view of what drives evolution.
Scientists have long known that the evolutionary changes that alter a species' appearance or create new species frequently occur in rapid bursts. One widely accepted theory holds that any evolutionary change results from a random switch of a single genetic unit within DNA.
These single-point mutations occur in about 1 out of every 100 million DNA sites each generation. This frequency is too low to cause rapid evolutionary change, assert John W. Fondon and Harold R. Garner, biochemists at the University of Texas Southwestern Medical Center at Dallas.
While examining human-genome data, Fondon found that small segments of repeated DNA sequences, called tandem repeat sequences, are frequently present in genes that control how an animal develops into its final appearance. Unlike single-point mutations, tandem repeat mutations occur when a cell's machinery for copying DNA makes a mistake and inserts a different number of sequence copies.
Such mistakes, which happen 100,000 times as often as single-point mutations, could alter an organism's appearance or function for successive generations.
"I was stunned by what I found," says Fondon. "It occurred to me that this might be a nifty way for [organisms] to evolve very rapidly."
To evaluate this hypothesis, Fondon and Garner looked for tandem repeat sequences in 92 breeds of domesticated dogs. For example, they examined a gene that determines nose length. They found that the number of times a particular sequence is repeated correlates strongly with whether a breed has a short or long muzzle.
Many researchers explain dog-breed diversity as the emergence of hidden traits in the genome. However, says Fondon, a more likely scenario is that genetic mutations occur in dogs at a high rate.
By comparing skulls of dogs over decades, Fondon and Garner found significant and swift changes in some breeds' appearances. For example, between the 1930s and today, purebred bull terriers developed longer, more down-turned noses.
Moreover, the researchers found more variation in tandem-sequence repeat lengths among dogs than they found in the DNA of wolves and coyotes.
These results suggest that dogs have experienced significantly higher rates of tandem repeat mutations than the related species have, says Fondon. Because tandem-repeat sequences litter the genes that control the developmental plan in many species, Fondon suggests that mutations in these regions could have a strong bearing on evolution.
"As a new finding about the biology and genetics of dogs, I'm all for it. But in terms of applying this to [evolution in general], I think there's a question mark," says Sean Carroll, an evolutionary geneticist at the University of WisconsinMadison.
Carroll notes that because dog owners have coddled their companions over the centuries, mutations that would have killed wild animals may have persisted in the gene pool of domestic dogs. Because domestication diverges from a standard model of evolution, he says, further experiments are necessary to add weight to Fondon and Garner's theory.
> The Big Bang is a creation event.
And your evidence that the universe was created by an intelligence is.......
Waiting.....
LOL, weak.
So you're saying your evidence of a creator of the universe is weak? On that we can agree.
If you actually find some, though, let us all know.
You're absolutely right- the only time I've been bitten by a dog- it was a little rugrat!!
I guess I just think God is a better cook than you and knew exactly what He was going to get when He set the whole thing in motion, from the Big Bang, to the asteroid, to Calvary.
Of course, He has the advantage of being omipotent, omnipresent, and existing outside of Time itself (alpha and omega), so I would expect no less.
It would appear that Shrek's maternal grandfather didn't have male pattern baldness....
Saruman did it first...
"We had many of these half-orcs to deal with at Helm's Deep."
There are two errors in this picture:
1) No pancake on the Bunny's head.
2) No Viking helmet on the Kitten!
I just gotta ask, you piqued my curiosity.
Did he chomp the Rott's balls from underneath, or what?
"The Bustard is an exquisite fowl/
With minimal reason to growl/
It escapes what would be
illegitimacy/
By the grace of a fortunate vowel."
That wasn't quite how he rendered it, I just googled the above on "Bustard" and "illegitimacy" together. But I remember him saying he was particularly impressed by the single-word fourth line...
During the Civil War, most breeds of dogs that are common today didn't exist. Most were developed in the late 19th century or in the 20th century.
It is like how scientist recently showed that the Red Sea can naturally part --- certain wind conditions, tides, and all that. "No miracle!" some cry. "Heresy!" cry others. Well, the miracle was not the parting, the miracle was parting just as Moses showed up with Pharoah on his tail, and then closing back up. I am quite sure God put the wind, tides, etc, in motion a million years ago to get that one just right.
Same with evolution. He created just the exactly right conditions for things to be as he wanted.[...]
Yes, God could intervene and bypass His rules of nature. But why? He made the rules. He knows how they work. Why should he not follow His own rules? So to answer your quandry: "we would never know which species evolved purely from evolutionary mechanisms, and which were given a helping hand by the Creator" This assumes God made a mistake in putting the Universe in motion. ALL were given the exact helping hand by God --- be it by a timely asteroid killing dinosaurs just as those mamals got going, or by parting the Red Sea at the right time. I do not presume that God would make a mistake. I presume He did it right and it is exactly as He designed it.
Very well said. Or, in the words of the Talmud, kol hanissim b'derech hateva, "all miracles happen in a natural way."
Now if it were an IRS-worker's dog, he'd have had intercourse with the other three mutts, just for swank!
Full Disclosure: Insert your own "screwing the pooch" joke here.
LOL!
Under what temperature, pressure, and concentration?
Oxygen molecules, atoms, or ions?
Hydrogen molecules, atoms, or ions?
Double-check your rate constants, not just equilibrium constants...
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.