Okay, everybody knows and accepts adaptation. That's easily observed and tested. That's not the question. The question is how does a DNA strand suddenly have a new base pair and how does the theory of evolution take into account the theory of genetics at that point. Because in order for an organism to go from having 10 base pairs to 11 base pairs is one Hell of a mutation. The problem roots itself in the three principles in genetics of:
1) When two members of the same species reproduce, they create a third member of the species. (This is why dogs don't have kittens)
2) When two members of different species reproduce they create nothing. (This is why there are no centaurs in TJ or West Virginia)
3) When you change the number of base pairs you change the species.
How does evolution over come this? It seems it would have to violate the first and third rule in order to have a "mutation" come about that have an extra base pair. It would either then have to violate the second rule or would have to have a staggering number of births within a concentrated area for them to be able to reproduce in. So basically, all the people in, say, NYC would have to suddenly be born with 24 base pairs. The statistical odds of this happening would make the likelyhood of Mary being born an XY female with a crude uterus releasing a self fertilized egg actually probable.
An this statistical odd and violation of genetics has had to have happened at least what, 15 times? (tobbacco has at least 25 IIRC) How is that possible? I just don't understand how that's possible.
The addition of base pairs changes the proteins that are made. DNA is mainly a blueprint for the production of proteins, proteins that keep your body functioning and moving as it should. It does this through the use of codons, which is the sequence of nucleotides in the base pairs.
If it is for the betterment of the organism, then nothing bad will happen. If the additional base pairs fucks up the amino acid sequence in the proteins, then the mutation will likely cause the organism to die.
Below is what a--pulled out of the ass--nucleotide sting would look like. Every 3 nucleotides is marked off into a codon.
AAG|TAC|GTT|AGT|AAG|CGC|ATG|GCT|AGC...and on until the end.
There is a specific start and stop combination, but I forget exactly what they are. Either way, messing with this order, either by changing a base pair, or adding a base pair (which happens around every 1/10,000 time a DNA strand replicates--for when cells divide) is mutation. As above, mutations that don't affect you adversely go largely unnoticed. You have probably accrued thousands of mutations in your body alone simply from this process.
The reason you aren't dead now from saturation of screw-ups in your DNA is because the codons (the sequence of 3 nucleotides, as detailed above) have many ways to code for a single protein. I forget, again, the combinations, but AAG and TAC and AGT could, in potentia, all code for the same protein to be added (this is probably not true, but again I forget which codons code for which amino acids).
Changing the number of base pairs could, over a long period of time, change the species. However, considering the amount of mutations happening almost every day, it's safe to say that there are a few strands of DNA within your body that have a few more base pairs than normal.
For further reading, and where I got my impromptu reacquaintance with codons and DNA from, check this:
TheBlackCat over at Bad Astronomy and Universe Today Forums
Well, there are a number of mechanisms. It is true that adding a base pair in a part of an unique gene that is coding for a protein will almost always render that protein inoperable. However, this is only a case if both those conditions are met. There are a number of situation in which that might not be the case.
First, the simplest is when there are multiple copies of the same gene. There are mechanisms which I am not very familiar with by which individual complete genes may be duplicated in a life-form's genome (I should be learning them soon). These include various proteins that duplicate segments as well as crossing over, a mechanism by which genes can shift from one chromosome to another. Obviously, once a gene has been duplicated one copy of the gene can mutate all it wants without affecting the cell's ability to make the protein, since the other copy of the gene can still produce sufficient amounts of the protein to supply the cell's need. This, as I understand it, is thought to be the mechanism by which the clotting cascade evolved. Parts duplicated, then mutated to catalyze the triggering of the original. Then these parts duplicates and mutated to catalyze the formation of the new molecule. Repeat several times and you have a cascade where each stage catalyzes the triggering of the next stage.
Another mechanism involves introns and exons. In eukaryote (i.e. not bacteria) DNA, the actual DNA code is usually not the final code that is read to make the protein. The DNA is converted into RNA, then parts of the RNA are removed and the remaining bits recombined to form a new RNA sequence. This shorter sequence is then read to make proteins. However, which sections of a given RNA are deleted and which are kept is not always the same. Sometime some sections of the RNA are kept, and other times other sections are kept. This way a single RNA, and thus a single gene, can code for a wide variety of proteins. Not all possible versions of the final RNA are useful, some have formed that do not code for anything and thus changes to those sections do not adversely affect the organism (unless they begin coding for something toxic) This means parts of a gene can grow, shrink, and change freely without altering the function of other sections. If these mutations suddenly make something useful, then the organism has a new, useful protein. I am not exactly clear on whether all combinations are synthesized or only specific one, or if it varies depending on the gene. Some sections may have to undergo some change to be recognized as useful sections.
Finally, for most eukaryotic organisms there are two copies of most genes. That means one gene can be mutated while still allowing the other to function normally. If this change on its own does not impede the function of the organism it can be what is called a "recessive" allele, an allele that only come into affect if two copies of the gene are present. This way you can get mutant genes without adversely affecting the organism, assuming the organism only has one copy of the gene. If the organism has two copies, they cannot produce the normal protein and can die as a result. Most human genetic disorders are of this sort. Because they only affect a small proportion of the creatures carrying them, they can persist in the population for long periods of time and can mutate freely during that time, possibly forming something useful. Some of these genes are lethal if an organism has two but can be helpful if an organism only has one. For instance, malaria cannot survive in people who have one sickle-cell anemia genes, but the people are not significantly affected by it. Likewise, people who have a single cystic fibrosis gene appear to be resistant to the bubonic plague and typhoid fever, even though they are not significantly harmed by the gene. However, these genes are lethal if someone has two copies.
I am not sure based on your post if you know this or not, but there is something to keep in mind with DNA. Every possible combination of 3 DNA bases has a corresponding codon that goes with it. The DNA is what is called "degenerate", there are usually several different DNA triplets that code for a certain amino acid. So no matter what triplet you put together, you will always find either an amino acid or stop codon that goes with it. The problem is that adding or deleting base pairs (called frame shift mutations) will alter every codon after them (assuming they are not done in a multiple of 3). This is because it the starting and stopping point of each codon changes.
Say you have a sequence like this:
Starting from the first base, the triplets will be as follows
Say, however, you add a new base after the 5th one:
The triplets will now be as follows:
As you can see, every codon after the addition has been completely changed. This means it is most likely every amino acid has also been changed. Frame shift mutations are very serious, and it is unlikely they could be viable in a coding segment of DNA unless they occurred near the very end of the gene. This particular change actually causes the fourth codon to change from coding for a serine amino acid residue to coding for a "stop" codon, which would cause the ribosome to stop synthesizing the protein completely and thus terminate the protein after only 3 amino acids have been added instead of the dozens, hundreds, or even thousands normally found in proteins. This is a common problem with frame shift mutations. (that stop codon was not intential, BTW, I just types in a random series of bases and that is what happened)
Hope this helps.
It's also EXTREMELY important to note that changes within the body's cells DO NOT affect the gametes (i.e., sex cells). Eggs and sperm do their own things in complete autonomy from the main body. Gametes are separated from the main body sometime during development in the womb (I think) and so whatever mutations you have at birth your gametes will carry. By that same token, whatever mutations you accrue over the course of your life WILL NOT alter, in any way, the DNA carried in your gametes.
Horseboy, I think you also have "base pairs" confused with "chromosomes", which are two completely different beasts. From Wikipedia, of all places, "The haploid human genome (23 chromosomes) is estimated to be about 3 billion base pairs long and to contain 20,000-25,000 distinct genes." Chromosomes hold the DNA strands, which in turn are themselves the long chains of base pairs of nucleotides. So yes, if there are more than the normal number of chromosomes, bad things happen. You may not even be born--alive and working, that is--if you wind up with more or less than the normal number of chromosomes. However, like stated above, DNA mish-mashing is quite normal.
EDIT: added some more Wiki pages.