How well do we understand DNA?

Hi T.Lit.I’ve been meaning to get involved in this topic in a while, and I keep on forgetting — drat!
Although LM, Q and WK (and others) have been fairly comprehensive in their comments (and have done a much better job than I would have done ), can I make a couple of comments regarding using this as a workable model for an intelligent driving force behind mutation?1) As far as I remember the DNA rearrangements which occur in B-cells (and T-cells) are permanent events. A potential B-cell which is not fully differentiated has the potential to make all of the different possible combinations (this is why you do get such a variety of antibodies). Once the cell has matured however, the other possible sequences have been excised from the genome — there is no going back. From what I can gather about Behe’s ideas, this is not incompatible with a super-dooper multi-fate Ur-cell at the beginning of evolution, which contained all of the information required for life. As a working model this doesn’t work for me. The first cell would not only have to contain DNA code needed to make a human, but also to make a crocodile, a banana, a fir tree and everything else on earth — that’s one hell of a cell!!2) I don’t know if you’re aware, but B-cells also undergo what is known as somatic hypermutation, whereby the piece of DNA which encodes the binding site of the antibody is very prone to DNA copying mistakes. It’s not fully understood how this hypermutation occurs but it has something to do with the recruitment of a defective DNA repair process to those areas. This seems to be the kind of mechanism you are proposing with your ‘intelligent programmer’ scenario, where mistakes are encouraged in certain areas and not others. I won’t labour this point because others have already mentioned it, but this is an important crutch of the ID movement that intelligence is detectable. This kind of mechanism is well within the reaches of random mutation and selection so how would you detect the hand of a designer/programmer in your theoretical model?Hope all that wasn’t too garbled

Hello again, TheLit.Sorry (again) for the appalling delay in replying — I should have warned you how lazy I am A couple of points: I’m not entirely sure you can do this very successfully. The mechanism you're proposing is based on an Intelligent Designer after all . But I appreciate that you don’t want to get dragged into ‘ID is not science’ debate. I’ll try not to stray too much.Having said that: Now I know other people have expressed similar opinions to mine in the past, and that this has the potential to goOT pretty rapidly, but:I think the reason he has proposed this model is that, as a biochemist he cannot deny the extremely good evidence for common ancestry, but still needs to propose a mechanism that allows the intervention of a Designer. So there’s the choice between an implausible Uber-cell or have a simple genome in which the random mutations are about as targeted as a flamethrower. It’s something that you need totackle.Of course if you don’t accept common ancestry then that’s yet another topic The trouble with this is that all of the ways that mutation occurs are essentially copying errors: from point mutations to duplications and large scale rearrangements. Any differences in the rate of mutation can be explained by natural processes (as Crashfrog and PS have pointed out).Also, don't confuse lack of mutation with conserving vital sequences by natural selection. There are sections of vital genes which are highly conserved between species, but the mutation rate may be just as high as elsewhwere in the genome. It's just that any organism which does have a mutation in those sections doesn't normally hang around for very long. Just a thought.Hope this hasn't come too late, and is not too repetative.