Posted on 08/25/2004 10:14:24 AM PDT by Michael_Michaelangelo
DNA mutates, and it's a good thing it does. If it didn't, there could only be one kind of life, not the millions there are today, and species could not adapt to new challenges. This is because mutations in genes—the coding portion of DNA—are the raw material for evolution. However, genes make up a surprisingly small fraction of our DNA. If the genome were a cookbook, its 30,000-odd genetic recipes would be scattered among millions of pages of apparently meaningless nonsense.
Mutations affect all DNA, not just the genes, and this provides population geneticists with a veritable toolbox of methods useful, for example, in DNA profiling. Importantly, all these methods rely on the idea of a “molecular clock,” the notion that mutations rain down on noncoding DNA like a fine drizzle, so constantly that genetic similarity is a good measure of evolutionary time. Thus, if orangutans diverged from humans twice as long ago as did chimpanzees, on any given piece of DNA we would find twice as many differences between the orangutan sequence and the human sequence as between humans and chimps. The mutations are marking time.
If the molecular clock works, scientists can do wonderful things like estimating how long ago it was that the common ancestor of all humans lived, or when birds evolved from dinosaurs. The clock assumes that mutations occur independently of each other and at a constant rate. By analyzing thousands of noncoding DNA sequences scattered throughout the human genome, Edward Vowles and William Amos have found that the clock is anything but constant. Instead, a mutation in one spot in the genome affects the chance of getting another mutation nearby.
Not all noncoding DNA is made up of benign tracts of random letters. Some sequences appear to be more difficult to copy than others, and these trouble spots can give rise to alphabetic stuttering. DNA is made up of four component chemical units, called nucleotides, which are often referred to by their initial letters: A, C, G, and T. Stuttering occurs when the same pairs or triplets of letters occur together, for example ACACAC. Such regions are called microsatellites, and instead of mutating by swapping one letter for another, as most nucleotides do, these sequences evolve mainly by gaining and losing triplets or pairs like “AC.”
In this study, Vowles and Amos used the published sequence of the human genome to track down and compare thousands upon thousands of microsatellites. If the molecular clock ran smoothly, they would expect to find no similarity at all between the DNA sequences surrounding any pair of unrelated microsatellites. To their surprise, they found the complete reverse, with entirely unrelated microsatellites showing widespread and obvious similarities in their flanking DNA. This meant that mutations near microsatellites were not random, but favored certain letters in certain positions. Just as a new shipwreck will attract its own special community of marine life, so microsatellites appear gradually to change the surrounding DNA towards a common pattern. The result is convergent evolution, an unusual state of affairs where, as time goes by, DNA sequences become more similar, not less.
As yet, the exact mechanisms remain unclear, though it probably has something to do with how comfortably different combinations of letters sit next to each other. In English, “U” always follows “Q” and “B” never follows “V.” Similar rules may apply to DNA, albeit on a much subtler level. For example, if a microsatellite contains alternating As and Cs, the flanking regions also tend to have As at alternate positions, in phase with the As in the microsatellite. It is as if the DNA prefers the pattern in the microsatellite to extend into the flanking DNA, rather than abruptly stopping at the end of the microsatellite.
These findings suggest that it may be wise to take the notion of a molecular clock at face value. With a perfect clock, two or three identical mutations would be highly unlikely, but we now know that this may be possible near microsatellites. Vowles and Amos estimate that as much as 30% of the genome may show evidence of convergent evolution, simply because microsatellites are so common. These mutation biases probably exist to a lesser extent in most sequences. Once scientists understand more fully how and where these biases operate, they may be able to estimate more accurately the risk of any given mutation occurring, be it one that causes human disease or makes a virus more virulent. These findings represent yet another windfall from the Human Genome Project, and act as a powerful reminder that unexpected results always lurk around the corner as we delve deeper into the secret world of the genome.
Sometimes you have to stick your finger in it every once in a while just to see if it's still there.
It's not at all the same as "I can just tell." If your wife (friend, son, whatever) tells you something, and I ask you how you know such-and-such, and you say, "My wife made that clear," that answers the question. That's not the same thing as your saying, "I can just tell."
In what way has God made Himself known? In many ways, of which I responded with one, since it's one knowable by everyone: by the things which He has made.
DNA is not what scientists seem to think it is. It is not the building blocks of life, it is not the plans for building life forms. It is only a couple of switches for a couple of features in an otherwise much more complex machine.
A bit of knowledge about data and the complexity of living organisms.
Astounding!
As you suggest, Wonder Warthog, evolution/gene mutation does seem to go hand in hand with added stress. A microbial evolutionist here at MSU separated a culture of bacteria into three separate cultures a decade or so ago and has followed their evolution/ gene mutation through about 30,000 generations. Their evolution does seem to be punctuated and stress-induced. Interestingly, the three separate cultures of the same bacteria have had different gene mutations that allow it to cope with the same stressor. The different cultures are evolving in different ways to deal with stresses to their environment. Pretty amazing.
I am a chemist, and that happens all the time.
WOW! Veeerrryyy interesting. Thanks for the info.
Ad hominem alert:
Since you are so fond of bible verses, I thought I'd throw one your way:
Deuteronomy 19:28
Ye shall not make any cuttings in your flesh for the dead, nor print any marks upon you: I am the LORD.
PS, love the picture in your profile!
I will be more specific,
God, the God of the Bible so that the phrase 'this God' in unneeded, indwelt me with the Holy Spirit and I began to speak in unknown tongues, just as is written in the Scriptures. I tell you I felt the Spirit well up from my innermost being. It felt great.
Years later a young man whose parents were concerned about his drug use sent him to see me. He was already a believer, but this was an obstacle. We prayed, and he also received the Holy Spirit with the sign of speaking in unknown tounges. He said it felt so great that he realized that drug use was just a cheap imitation of the feeling he got from the Holy Spirit- that this was the real thing.
The euphoria does not continue, but the speaking in unknown tounges does.
My grandmother was healed from lupus. I remember how frail she was in 1988 when I was home on leave from the military. I remembered thinking that it would be the last time I saw her alive on Earth. She is still alive today and she has a doctors report saying that she does not have a trace of lupus.
My step-brother in law was in a car wreck as a teenager, He had to wear a leg brace because his leg was crooked. A preacher prayed over him and do you that his leg straightened out that very day. Right in front of his family. They threw the leg brace away- it did not fit from that moment forward because his leg was straight and remains so to this day.
These are events from my life but many such events are recorded in the Bible. Read the 53rd chapter (or is it 51?)of Isaiah and realize that this man was a prophet of the living God speaking of Jesus Christ. The Bible is full of fulfilled prophecy. In fact, that is how they got to be in the bible- that is how they got to be acknowledged as really representing God.
Perhaps no amount of testimony will convince you. Perhaps you will dismiss it all. If so, this is not a head problem, but a heart problem.
BWAHAHA! Delicious!
They profess NO shame, but they do have mighty quick fingers on the Abuse button.
"Festival of Abuse Button Mania" placemarker
...or all the schooling in the world will not keep a large fraction of the population from being pig-ignorant. No offense.
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