>>12784215I think this is a good summary. To add to this, a gene can induce expression of a gene product and is heritable but a gene product can't induce expression of a gene and is not heritable.
mRNA has situations where it can be a gene or a gene product. In most cells and organisms, mRNA is a gene product, because it is produced from a DNA genome and it is not heritable, because it can't be used to produce RNA or DNA, which would result in its replication. This is because most cells lack reverse transcriptase, which synthesizes DNA from RNA, and RNA-dependent RNA polymerase, which synthesizes RNA from RNA.
Within retroviruses, the presence of reverse transcriptase enzyme makes RNA and mRNA into a gene, because the virus can use it to make a gene product cDNA. Also, within a retrovirus, RNA and mRNA are heritable because the virus possesses RNA-dependent RNA polymerase, allowing RNA replication. Finally, within a retrovirus itself, the gene product cDNA can't be used to produce the gene RNA because retroviruses lack DNA-dependent RNA polymerase. This is why they need host cells that have it, since they also lack ribosomes that work off the modifications by this specific polymerase.
So putting this together, mRNA, within a human cell, is normally a gene product, but if reverse transcriptase and RNA-dependent RNA polymerase are introduced to the cell (by a virus), mRNA/RNA can become a gene (a viral gene) because it now has the means to both produce a gene product and become heritable.
But, in the case of the vaccine, since the vaccine does not directly introduce reverse transcriptase or RNA-dependent RNA polymerase into a human cell, nor does it trigger their production, the particular mRNA sequence introduced is not heritable, can't reproduce into RNA or DNA, and is therefore not a gene.
I mention DNA or RNA only here as means of heritability because to say protein is heritable violates the central dogma of molecular biology.
That sum up everything?
