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Initially, the term "gene" referred to abstract concept of inherited trait.

Currently this term was hijacked with molecular genetics and means a continuous sequence of nucleotides. However, it omits the fact that for a phenotypic trait to be inherited, sometimes there can be more than one sequence of nucleotides, and sometimes one sequence of nucleotides participate in the formation of more than one phenotypic trait.

Is there a single-word term describing non-DNA "Mendelian gene"?

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    $\begingroup$ Welcome to Biology.SE. How is any of what you are describing non-DNA? Please edit your post to be clearer and make sure you demonstrate that you've done the expected prior research. Please also take the tour and consult the help center starting with How to Ask a good question on this site and make changes to your post accordingly. Thanks! $\endgroup$
    – tyersome
    Jun 4, 2021 at 4:54
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    $\begingroup$ @tyersome I replaced "sequence" to "continuous sequence". However, there are also phenotypic traits that even do not completely depend on DNA sequences, even if they conventionally claimed by the molecular geneticists to be derived from some continuous nucleotide sequence (which is nowadays called "gene"). For example, if the child will not learn language to a certain age, he will lack the phenotypic trait of speech. If he missing any of (non-continuous) nucleotide sequences responcible for development of vocal cords, he will also not be able to produce speech. $\endgroup$
    – user268587
    Jun 4, 2021 at 5:10
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    $\begingroup$ @user268587 You seem to be referring to a polygenic trait, not a "non-DNA" trait (multiple genes affecting a single trait). The opposite, a pleiotropic gene, is where one gene affects multiple traits. $\endgroup$
    – Armand
    Jun 4, 2021 at 8:34
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    $\begingroup$ Epigenetic inheritance is one example, but it is not covering all the possibilities. en.wikipedia.org/wiki/Transgenerational_epigenetic_inheritance I suggest reformulating the question in less controversial terms: less attacks on the established terminology, and more about non-genic inheritance. $\endgroup$
    – Roger V.
    Jun 4, 2021 at 11:41
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    $\begingroup$ Please remove the phrase “non-DNA” from your question. The only non-DNA genes are RNA genes in certain viruses, which is not what you mean. The nucleotide sequences you describe are DNA — by definition. Specific descriptive terminology is used for genes which encode subunits of a protein, both of which are required for a functional whole (1) or generate more than one product by differential splicing (2), but it only makes sense to answer your question in these terms if you transform it into something that makes sense. “Answer only well-asked questions” is a principle of this site. $\endgroup$
    – David
    Jun 4, 2021 at 17:31

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I think that what you are interested in is the original Johannsen definition of the gene as of 1909 (I translated this article, caveat emptor). Notably, Johannsen cautioned explicitly against reading too much into the abstraction of the gene, and instead insisted on reference to heritable phenomena that we would call traits or phenotypic characters, with the understanding that underneath that there is an unseen and unknowable "genotype", which can be inferred through the use of logic and statistics.

However, as you rightly point out, molecular genetics came along and changed things. At that point, many of the phenomena that Johannsen was interested in could be directly be related to genes in the sense of DNA sequences. The Central Dogma of molecular biology reorganized thinking along molecular gene-centric lines, which do have issues as you note.

However, the original Johannsen definition of the gene was never more than a a vague factor for helping genetic reasoning, no one has ever observed such a thing in the wild! There is a reason why no one speaks of genes in this way anymore, and it's because we now know a lot more about how complex molecular mechanisms that generate phenotype are. This is one of the good things that molecular biology gave us, even if you take issue with its reductive character.

If what you want is just a term that refers to a character which can be built of many genes (e.g. polygenic), or including e.g. epigenetic inputs, then "phenotype" or "trait" is perfectly good. But again, such things are subjective, and are limited by what humans can measure and observe.

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The Cambridge Dictionary, CDC, and the NIH's institudes researching the human genome and cancer all agree that genes have 2 properties:

  1. they are associated with heredity
  2. they are a section of DNA translated into proteins

However, the Oxford Dictionary has an informal definition and formal definition. The informal definition refers to only to the first property and the technical definition refers to only the second. It also agrees with you on the etymology of the word.

It is clear to me that in the modern usage, gene refers to one factor in the inheritance of traits. The definition does not assume that no other factors of trait inheritance (e.g. DNA methylation, memes) exist. This differs from the early 20th century use of the word, which assumed that no other factors besides genes are responsible for inheritance, i.e. 'gene' was an inclusive term for all factors of inheritance.

To my knowledge, there is no single word in modern usage that has the same definition as 'gene' did in the early 20th century. The phrase 'factors of inheritance' is as close as I think you can get.

P.S. Technically detail, but not all continuous sequences of nucleotides in a strand of DNA are genes. Many sections of DNA serve structural purposes (e.g. centromeres, telomeres) or help regulate gene expression.

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    $\begingroup$ There are some exceptions to your (2): for example, some viruses encode their genes in RNA rather than DNA. More importantly, many genes are not translated into proteins -- their RNA transcript is the functional unit: for example ribosomal RNA genes or transfer RNA genes. Other parts of genes (such as promoters and introns) are either not transcribed or not translated, but help determine the transcribed or translated product. $\endgroup$
    – Armand
    Jun 4, 2021 at 7:53
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    $\begingroup$ Thus, a more complete version of your technical definition (2) above would be: "a distinct sequence of nucleotides forming part of a nucleic acid segment, the order of which determines the order of monomers in a polypeptide or nucleic acid molecule which a cell (or virus) may synthesize." (minor modification of Oxford Languages definition returned by Google) $\endgroup$
    – Armand
    Jun 4, 2021 at 7:53
  • $\begingroup$ Your right. What is interesting though is that of the 5 sources I had for definitions, only the Oxford Dictionary includes viral RNA as containing genes. The rest make explicit reference to DNA. $\endgroup$
    – E Tam
    Jun 4, 2021 at 15:51
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    $\begingroup$ General dictionaries are a useful reference to the English language, and I would quote them on SE English language and usage, but they are hardly where one goes to discover the terminology used in specialist aspects of a subject. This is trivially obvious from definition 2, which ignores both RNA viruses and non-coding parts genes and mRNAs. $\endgroup$
    – David
    Jun 4, 2021 at 17:39

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