genes are like atomic nuclei in how they determine macroscopic structures

An example of analogy used in popular science writing:

"If a highly simplified physical analogy is to be permitted here, we may compare the relation between the genes and the living organism with the relation between the atomic nuclei and the large lumps of inorganic matter. Here too, practically all physical and chemical properties of a given substance can be reduced to the basic properties of the atomic nuclei that are characterised simply by one number designating their electric charge. Thus, for example, the nuclei carrying a charge of 6 elementary electric units will surround themselves by the atomic envelopes of 6 electrons each, which will give these atoms a tendency to arrange themselves in a regular hexagonal pattern, and to form the crystals of exceptional hardness and very high refractive index that we call diamonds. Similarly a set of nuclei with electrical charges 29, 16, and 8 will give rise to the atoms that stick together to form soft blue crystals of the substance known as copper sulphate.[*] Of course, even the simplest living organism is much more complicated than any crystal, but in both cases we have the typical phenomenon of macroscopic organisation being determined to the last detail by microscopic centres of organising activity."

George Gamow (1961) One, Two, Three…Infinity. Facts and speculations of science, Revised Edition, Dover Publications, Inc., New York.

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[* Note: copper sulphate is an ionic substance, containing copper and sulphate ions, not atoms. The blue crystals (which never seemed especially soft to me) are of the pentahydrate, CuSO₄.5H₂O, so also contain water molecules (and therefore hydrogen nuclei) in the lattice.

Carbon does have"a tendency to arrange … in a regular hexagonal pattern" in graphite, but in "the crystals of exceptional hardness and very high refractive index that we call diamonds" it has a tetrahedral arrangement.]