The whole truth
Posts: 1554
Joined: Jan. 2012
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| Quote (Otangelo @ Nov. 19 2015,07:34) | | Quote (NoName @ Nov. 19 2015,06:42) | | Why is abiogenesis impossible? |
I'll give you another example.
Topoisomerase II enzymes, amazing evidence of design
Complete and equal transmission of DNA to daughter cells is crucial during mitosis. During cell division, each daughter cell inherits one copy of every chromosome. The metaphase-to-anaphase transition is the critical point in the cell cycle where the cell commits to separation of sister chromatids . Once spindle attachment is complete, cohesion must be eliminated to enable the physical separation of sister chromatids. This requires cleavage of the protein complex cohesin by separase and, in some instances, completion of chromosome decatenation. Catenation is the process by which two circular DNA strands are linked together like chain links. This occurs after DNA replication, where two single strands are catenated and can still replicate but cannot separate into the two daughter cells.
II Topoisomerase enzymes is a ubiquitous enzyme that is essential for the survival of all eukaryotic organisms and plays critical roles in virtually every aspect of DNA metabolism. It performs the amazing feat of breaking a DNA double helix, passing another helix through the gap, and resealing the double helix behind it. They are essential in the separation of entangled daughter strands during replication. This function is believed to be performed by topoisomerase II in eukaryotes and by topoisomerase IV in prokaryotes. Failure to separate these strands leads to cell death. As genetic material DNA is wonderful, but as a macromolecule it is unruly, voluminous and fragile. Without the action of DNA replicases, topoisomerases, helicases, translocases and recombinases, the genome would collapse into a topologically entangled random coil that would be useless to the cell. The topoisomerase is thought to be a highly dynamic structure, with several gates for entry of DNA into the two DNA-sized holes. Loss of topoisomerase activity in metaphase leads to delayed exit and extensive anaphase chromosome bridging, often resulting in cytokinesis failure, although maintenance of limited catenation until anaphase may be important for sister chromatid structural organization 9 Accurate transmission of chromosomes requires that the sister DNA molecules created during DNA replication are disentangled and then pulled to opposite poles of the cell before division. Defects in chromosome segregation produce cells that are aneuploid (containing an abnormal number of chromosomes)-a situation that can have dire consequences.
Like many other enzymes, topoisomerase II are essential for cell function, and had to be present in the first living cell to exercise their function right in the beginning, when life began.
Within each chromosome, two dimensions of organization are at play: condensation along the axes ensures the entire chromatid, end-to-end, is kept together 8 , while the tight association of sister chromatids until anaphase, termed sister chromatid cohesion (SCC), ensures that each daughter cell receives only one copy . Two mechanisms are known to play a role in SCC: DNA catenation, which physically interlocks (catenates) DNA across the sister chromatids ; and protein linkages through the cohesin complex, which physically tether the sister chromatids to one another.
Topoisomerase II forms a covalent linkage to both strands of the DNA helix at the same time, making a transient double-strand break in the helix. These enzymes are activated by sites on chromosomes where two double helices cross over each other such as those generated by supercoiling in front of a replication fork
Once a topoisomerase II molecule binds to such a crossing site, the protein uses ATP hydrolysis to perform the following set of reactions efficiently:
(1) it breaks one double helix reversibly to create a DNA “gate”;
(2) it causes the second, nearby double helix to pass through this opening; and
(3) it then reseals the break and dissociates from the DNA. At crossover points generated by supercoiling, passage of the double helix through the gate occurs in the direction that will reduce supercoiling. In this way, type II topoisomerases can relieve the overwinding tension generated in front of a replication fork. Their reaction mechanism also allows type II DNA topoisomerases to efficiently separate two interlocked DNA circles. Topoisomerase II also prevents the severe DNA tangling problems that would otherwise arise during DNA replication. The enormous usefulness of topoisomerase II for untangling chromosomes can readily be appreciated by anyone who has struggled to remove a tangle from a fishing line without the aid of scissors.
These molecular machines are far beyond what unguided processes involving chance and necessity can produce. Indeed, machinery of the complexity and sophistication of Topoisomerase enzymes are, based on our experience, usually atributed to intelligent agents.
Type IIA topoisomerases consist of several key motifs: an
N-terminal GHKL ATPase domain
Toprim domain
central DNA-binding core
C-terminal domain
Each of these key motifs are essential for the proper function of the enzyme. No part can be reduced, and neither is it possible any of the subparts to emerge by natural means. Not only had the enzyme to emerge prior to the first cell being formed, and so could not be the result of evolution, but the sub parts by themself, and the enzyme by itself even fully formed, would have no use, unless the DNA double helix molecules were already existing as well, and so the whole process of cell division, mitosis, and catenation, which happens through DNA replication. The enzyme is however essential for life, so if Topo II is removed, life could not exist. So we have here one of inumerous essential seemingly tiny and aparently unimportant parts, which by closer looking reveal to be life essential. This provides another big question mark in regard of naturalistic explanations, provides on the other part ones more a powerful argument for design.
http://reasonandscience.heavenforum.org/t2111-t....gn#3754 |
Why are you pretending that scientific evidence matters to you? Could there ever be any scientific evidence that would convince you to discard your religious beliefs?
If it were discovered that there is a 'creator' but that it wasn't/isn't your chosen, so called 'God' and is nothing like your chosen, so-called 'God', would you discard your religious beliefs?
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Think not that I am come to send peace on earth: I came not to send peace, but a sword. - Jesus in Matthew 10:34
But those mine enemies, which would not that I should reign over them, bring hither, and slay them before me. -Jesus in Luke 19:27
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