I find several things wrong with this (and your paragraph on chimpanzees and humans).Ã‚Â You seem to be confusing form with content, the chromosomes being the 'form', and the genes the 'content'.Ã‚Â A lengthy novel may be published in multiple volumes, but regardless of the number of volumes, it's still the same story. The chromosomes are analogous to the volumes rather than to the story itself. There are a number of genetic disorders (thousands actually) that are caused by chromosomal abnormalities -- Down's syndrome being a well-known example -- but these are mostly analogous to 'volumes' being improperly distributed. The fact that individuals are able even to survive at all with these abnormalities suggests that there is more freedom for error than you appear to realize (Down's syndrome females have, though rarely, even been able to produce children).
How genes and chromosomes are built is what genetics is all about. From the early transcription of the DNA to the fully formed chromosome there are a number of checkpoints. Just before the cell completely splits during the anaphase is the spindle assembly checkpoint. Here the spindle must be built, the chromosomes must attached to the spindle and the chromosomes must aligned down the center. When the duplication process malforms it results in ASPM (abnormal spindle-like microcephaly associated) which results in a 70% reduction in brain size.
"The analysis of the most dramatic of these duplications, affecting 10% of human Chromosome 2, enabled a detailed reconstruction of the events leading to the appearance of a novel gene family. "
(Complex genomic rearrangements lead to novel primate gene function, linked below)
For this fusion (sorry about the typos earlier) to occur we are talking about no less the 22 gene duplications in a section covering 10% of Chromosome 2. You might be interested to know that Down's syndrome is due to the overexpression of genes. My point being that there are hazards to dramatic changes in the form and function of chromosomes. In order to put this into perspective lets try to grasp just what would have been effected and how:
"The eight members of this family originated from the highly conserved nucleoporin RanBP2 by several genetic rearrangements such as segmental duplications, inversions, translocations, exon loss, and domain accretion. "
Complex genomic rearrangements lead to novel primate gene function.
Ok, we have eight genes in a highly conserved region undergoing at least half a dozen genetic rearrangements. For a region to be considered highly conserved it must be very resistant to changes on this level and they seemed to have happened in a relativly short space of time. It seems to me that evolutionists would be in awe at the enormous changes that occured. As a creationist I am simply unconvinced that such changes are remotely possible without catastrophic conseqeunces like the ASPM gene and Down's syndrome.
And I'm not sure why you feel (if I correctly assess that as your implication) that such a splicing would necessarily take place at the centromere, or why it is 'damage to the spindle' that would be of primary concern; it seems to me that the spindle is much more likely to damage the chromosomes (that is, to botch their distribution) than to be damaged by them.
These changes were in close proximity to the centemere region. Bear in mind that these are just some of the more dramatic changes that would have had to occur, there are many others.In Chromosome 6 the centromere would have had to be moved not once but twice:
. "Contrary to this simple evolutionary scenario, however, the centromere was found to be located in three distinct regions, without any evidence of chromosomal rearrangement that would account for its movement. One of the two centromere repositioning events occurred in great apes ancestor."
Chromosome 6 Phylogeny in Primates and Centromere Repositioning
There is a reason that changes in and around the centromere can cause serious problems for the spindle alingment. If for whatever reason the centromere and the spindle don't line up properly the consequences can be devastating.
And random chance (by definition) couldn't possibly care a fig about what 'you want' anyway; if it doesn't work, it simply gets selected out.
Random chance has nothing to do with how genes and chromosomes are duplicated. Now the recombination of genes are another matter and there is a natural process by which traits derived from favorable combinations get preserved while less favorable one simply don't survive. The genes are not changed much at all but how they are expressed changes greatly.
And (sorry, but this is really bugging me) it's: fusion.
Sorry about that, I really should edit my posts more carefully.
Well, I wouldn't -- but you might be surprised at how liberally some taxonomists have been willing to apply the species distinction. Using infertility as the sole criterion is the most conservative apporoach. For many biologists, any barrier to interbreeding may suffice, such as a behavioral or geological barrier.Ã‚Â For them, it doesn't matter so much why two groups aren't interbreeding as long as it is clear that they aren't interbreeding (neither fertility nor infertility can always be regarded with confidence as all-or-nothing propositions anyway). It's a judgement call.
Actually, I would say it's like arranging the documents on your hard drive. You will organize then in such a way as to make them easier for you to use them. When Aristotle organized and classified animals in his own way that seemed fine untill the discovery of the New World. Then we had all of these different animals that had changed dramatically over time. I was reading a thing on the taxonomic classification of birds and it was interesting how simple or sophisiticated it could be. It all depends on what you are trying to organize into catagories. The more details you are organizing, the more complicated the taxonomic catagories will get. Taxonomic catagories are not objective, they are completly subjective. They are organized from the perspective of the observer and they are simply meant to make retrival easier.
In other words, taxonomy was made for man not man for taxonomy.