Most genetic research tries to establish a relationship between a certain genotype and certain phenotype.

To me this is like trying to understand a system as a black box, where you try to establish a relationship between a certain input and an output. It seems unnecessary to me because it seems possible - even tough extremely complex - to establish a more mechanical relationship between the box’s system and its environment and make a mechanical model that would always be correct about the box’s outputs based on a combination of inputs.

What is the missing link that impedes science from creating a model of genetics that is 100% certain of the resulting phenotype based on a genotype? Is it just lack computing power due to the complexity of understanding genotype/phenotype as mechanical system instead of probabilistic one?

  • $\begingroup$ Perhaps you could clarify what you understand phenotype to mean, and what the determinants of a phenotype are. $\endgroup$ – De Novo Mar 4 '19 at 6:39
  • $\begingroup$ The actual answer to this is in your question: "possible - even though extremely complex". Complexity both limits the current level of any science (as in, the more complex the system the more time it takes for scientists to figure it out. Consider the time it took between discovering DNA and sequencing the human genome for example), and even the level of understanding humans could ever realistically achieve (because chaos theory issues). But I think a good answer to this question would give examples of the current state of the science in terms of the mechanical genotype-phenotype relationship. $\endgroup$ – Oosaka Mar 4 '19 at 10:28
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    $\begingroup$ Many genes are not associated with phenotypes. Your question is not expressed in a contemporary manner. I have answered on the assumption that, in plain English, you want to predict what a gene does. $\endgroup$ – David Mar 4 '19 at 14:20

I’m not sure that this question is suitable for this list, which is intended for questions from students of biology, not questions from students of the physical sciences who would like biology to fit into the sort of framework they understand. However…

First, genetics has been variously defined throughout history — Wikipedia currently has “Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms”, but I do not think current research is concerned with “establish(ing) a relationship between a certain genotype and certain phenotype”. Phenotypes are not where it’s at.

I stand to be corrected, but I think the question behind the post can be put simply as:

Why can’t we predict the function of a gene and its product from the DNA sequence?

And the answer is simply:

Because the DNA sequence does not provide enough information for us to do that. For the benefit of the physical scientist I’d say it’s like trying to determine the value of several unknowns with an insufficient number of simultaneous equations.

Let me use some analogies to explain further.

  1. It’s like trying to assemble IKEA furniture without instructions.
  2. Or, worse, it’s like trying to determine the function of a single component of IKEA furniture without even knowing whether it’a part of a Rågifarsok or a Nässeltrjik.
  3. Or someone thinking that the instructions for a Nässeltrjik will tell you how to build a Rågifarsok.
  4. Or, if you don’t do IKEA, it’s like a person transported in time from the middle ages trying to guess what the blueprint for an internal combustion engine means.
  5. Or for the same person to guess what a screwdriver does.

That’s why biology is an experimental science.


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