Genome complexity: making haploid from diploid egg (Introduction)

by David Turell , Sunday, August 02, 2020, 19:55 (1362 days ago) @ David Turell

It is a very complex process of dividing chromosome which uses supposed junk DNA to guide it:

https://evolutionnews.org/2020/07/dna-may-be-junk-at-one-level-but-of-utmost-significan...

I mentioned that chromosomes can and do have roles that go far beyond the so-called “Central Dogma.” Nowhere is this point better demonstrated, it would seem, than in the phenomenon of meiosis or “reductional division,” which generates a haploid gamete from a diploid germ cell by means of an intricate series of developmental events. Indeed, it is during the latter stages of the production of an animal oocyte that many functionalities of what some disparage as “junk DNA” take center stage.

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Chromosomes that are about to undergo meiosis (or mitosis) have a distinct ensemble of functions that are grouped and harnessed ever so intricately into kinetochores, which are the “levers” of their maneuverings. These are “over and above” (indeed, epi– to) nucleotides have long been observed to be peculiar in their qualities. For one thing, they are dynamic platforms that have roles that are phase- or stage-specific. In the case of metaphase I, for example, those of one set of sister chromatids have to be in cohesion (or be paired) and jointly linked to one pole, while those of the other set of sister chromatids have to likewise be in cohesion (or be paired) but jointly linked to the opposite pole.

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What these two pieces of evidence suggest, then, is that what may be “junk” at one level may be of the utmost significance at another level. (my bold) This happens I think by way of a top-down causal process that Paul Davies (2012) has alluded to, explainable in part by the augmentation of:

the normal terms referring to local forces contained in the Hamiltonian for chromatin with additional (presumably small) non-local terms representing functional (i.e. semantic or contextual) information. By coupling the mechanical and informational dynamics in this manner, the dynamical laws describing chromatin behaviour would become time-dependent and change according to the informational state of the system. Information would then possess direct, albeit subtle, traction over matter and permit epigenetic control to be exercised directly on the chromatin itself. (my bold)

Such would involve an “explicit coupling between dynamical laws and information-rich states, thus endowing higher level entities, such as contextual information, with direct causal efficacy on matter alongside intermolecular forces.”

If we take such “contextual information” to be resident at all tiers of the meiosis I network, from the spindle as whole to (say) each and every centromeric locus, then “with direct causal efficacy” retroelement and satellite DNAs can be endowed with information-bearing states. Of course, “such a proposal represents a decisive break with the normal formulation of the theory of dynamical systems,” as Davies notes, which means that “theories of this sort remain largely unexplored.” But explore it we should…and especially where cytology meets “junk” DNA.

Comment: I have skipped over a highly complex description of the many protein parts of this mechanism. Note the two bolds. The first tells us, that junk DNA at one level, because it does not code for protein, has active duties elsewhere in the reproductive genome processes. The second bold notes the passage of information to the molecules to control the process. The final paragraph discusses that information and that much more research has to be done to explore how the information is utilized. The information drives the functions. Information implies a designing mind created the process.