sparc
Posts: 2088
Joined: April 2007
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gpuccio is the living proof that if intelligent design is true the intelligent designer occasionally makes stupid mistakes
which result in IDiots who stand out even among the other IDiots at UD | Quote |
6
gpuccio February 4, 2015 at 8:50 am
KF:
Thank you for the very good summary. Among many other certainly interesting discussions, we may tend to forget sometimes that functionally specified complex information is the central point in ID theory. You are very good at reminding that to all here.
I would like to suggest a very good example of multilevel functional complexity in biology, which is often overlooked. It is an old favourite of mine, the maturation of antibody affinity after the initial immunological response.
Dionisio has recently linked an article about a very recent paper. The paper is not free, but I invite all those interested to look at the figures and legends, which can be viewed here:
http://www.nature.com/nri........ft.html
The interesting point is that the whole process has been defined as “darwinian”, while it is the best known example of functional protein engineering embedded in a complex biological system.
In brief, the specific B cells which respond to the hapten (antigen) at the beginning of the process undergo a sequence of targeted mutations and specific selection, so that new cells with more efficient antibody DNA sequences can be selected and become memory cells or plasma cells.
The whole process takes place in the Germinative Center of lymph nodes, and involves (at least):
1) Specific B cells with a BCR (B cell receptor) which reacts to the external hapten.
2) Specific T helper cells
3) Antigen presenting cells (Follicular dendritic cell) which retain the original hapten (the external information) during the whole process, for specific intelligent selection of the results
4) Specific, controlled somatic hypermutation of the Variable region of the Ig genes, implemented by the following molecules (at least):
a) Activation-Induced (Cytidine) Deaminase (AID): a cytosine:guanine pair is directly mutated to a uracil:guanine mismatch.
b) DNA mismatch repair proteins: the uracil bases are removed by the repair enzyme, uracil-DNA glycosylase.
c) Error-prone DNA polymerases: they fill in the gap and create mutations.
5) The mutated clones are then “measured” by interaction with the hapten presented by the Follicular DC. The process is probably repeated in multiple steps, although it could also happen in one step.
6) New clones with reduced or lost affinity are directed to apoptosis.
7) New clones with higher affinity are selected and sustained by specific T helper cells.
In a few weeks, the process yields high affinity antibody producing B cells, in the form of plasma cells and memory cells.
You have it all here: molecular complexity, high control, multiple cellular interactions, irreducible complexity in tons, spacial and temporal organization, extremely efficient engineering. The process is so delicate that errors in it are probably the cause of many human lymphomas.
Now, that’s absolute evidence for Intelligent Design, if ever I saw it. |
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"[...] the type of information we find in living systems is beyond the creative means of purely material processes [...] Who or what is such an ultimate source of information? [...] from a theistic perspective, such an information source would presumably have to be God."
- William Dembski -
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