I was reading The Selfish Gene. In the 2nd chapter - "Replicators" I read:

Think of the replicator as a mold or template. Imagine it as a large molecule consisting of a complex chain of various sorts of building block molecules.

The small building blocks were abundantly available in the soup surrounding the replicator. Now suppose that each building block has an affinity for its own kind. Then whenever a building block from out in the soup lands up next to a part of the replicator for which it has an affinity, it will tend to stick there. The building blocks that attach themselves in this way will be automatically arranged in a sequence that mimics that of the replicator itself. It is easy then to think of them joining up to stable chain just as in the formation of the original replicator. This process could continue as a progressive stacking up, layer upon layer.

This is how crystals are formed. On the other hand, the two chains might split apart, in which case we have two replicators, each of which can go on to make further copies.

I don't get the part in bold.

  1. If these molecules joins the replicator then the replicator wouldn't change?

  2. To what refers with "The building blocks that attach themselves in this way will be automatically arranged in a sequence mimics that of the replicator itself"? A new sequence? The same sequence?

  3. In the part "It is easy then to think of them joining up to stable chain just as in the formation of the original replicator", what is it joined? replicator with this building block? these building blocks with other building blocks in the soup to form a copy of replicator?

  4. Why you can infer that is how the crystals are formed?

Take into account that I don't have a solid biology background, so it would be great if you can answer it in detail. I really appreciate your help!.

  • $\begingroup$ If you have a crystal of table salt, sodium chloride (NaCl), and place it in a saturated solution of NaCl in water, the salt crystal will start grow as the individual Na+ and Cl- ions in solution, settle on the face of the crystal, and enter the solid phase. In the example, the Cl- building blocks align to the Na+ ions in the crystal (so it is not “like with like”). $\endgroup$ – mdperry Jul 30 '18 at 16:33
  • $\begingroup$ So, Ci- ions joins the Na+? And what about the others Na+? $\endgroup$ – Gioconda Aug 1 '18 at 18:03
  • 1
    $\begingroup$ Check out this page: en.m.wikipedia.org/wiki/Sodium_chloride. Na+ attracts Cl- AND that means Cl- attracts Na+. $\endgroup$ – mdperry Aug 1 '18 at 22:16

This is how I think about it. Here is the original large molecule, with each of its 'parts' represented by a letter. There are a few different kinds of part:


As it drifts around in a 'soup' of parts, new parts stick to it one by one, like for like. Here it is after two parts stick to it:

  A         T

Here it is after a few more:

C-A   C   A-T   C   A

Eventually, all the parts have got a similar part stuck to them:


Now, if the two halves split, the molecule has replicated itself.

  • $\begingroup$ So, 1. The replicator, in fact, changes, but it can only contains copy of itself?. 2. The string just mimics the original sequence of replicator? 3. These building blocks are joining with others to form a copy of the original string? 4. When the replicator repeats his string multiple times, it converts in a crystal? Finally, just to confirm, duplicates of the replicator occurs when the replicator halves? $\endgroup$ – Gioconda Aug 3 '18 at 18:19
  • $\begingroup$ Yes to 1, 2, 3. For 4 I don't think he meant exactly that the molecule forms a crystal, but it was an analogy - the idea of one layer being built from another layer by joining like to like is similar to a salt crystal being built up. Finally, yes, when the replicator halves there are now two identical copies when there was only one before. $\endgroup$ – Jonathan Moore Aug 16 '18 at 13:23

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