If I remember correctly, it was Dawkins who argued that DNA is not a blueprint in a strict sense, but rather a recipe, in the sense that just by looking at the genes you can predict which phenotypes they will produce, but the process requires specific sequences of steps and on/off switching of genes, with the result that just by looking at the phenotype you cannot deduce what the genes looked like.
Yes. That was an oversimplification. In reality, what exactly will the DNA produce depends on... many things, probably even including small changes in temperature.
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