A and B are two different proteins: 1- can they have same mrna 2- is it possible that the gene types which encoding the synthase are same ?

my answer is yes to both . because after protein synthased cell can remove aminoacids with post-transcriptional modification etc.

  • $\begingroup$ It also depends on what you mean by the same mRNA? Same mature mRNA? The same transcript can be differently alternatively spliced, leading to different proteins. $\endgroup$
    – NatWH
    May 28 '18 at 12:25
  • $\begingroup$ What on earth is meant by "the synthase"? No synthase has been mentioned. And what is meant by "gene types". Please clarify the question, i.e. give it in full. And provide a better explanation of your reasoning for each part. $\endgroup$
    – David
    May 28 '18 at 14:38

1) Can two different proteins have the same mRNA?

This isn't clear enough to give you an answer:

  • Can two different proteins be made from the same mRNA molecule?
    • Yes, polycistronic mRNAs can encode several proteins which are translated separately (we can engineer this using internal ribosome entry sites, IRES).
    • Yes, different proteins can be translated from one open reading frame by failure of peptide bonding between two amino acids (we can engineer this using 2A peptide sites).
    • Yes, identical proteins can be translated from one mRNA and then modified differently after translation to yield different "final" proteins.
    • Yes, identical polypeptides can be translated from one mRNA and then incorporated in different protein complexes.
  • Can two different proteins be made from the same mRNA code?
    • No, not made in the sense of translated.
    • Yes, as above, identical proteins/polypeptides can be made and treated differently after translation.

2) Is it possible that the gene types which encode the synthase are the same?

Gene types? Do you mean genotype, i.e. allele? What synthase? Sounds like a homework question to me.

  • $\begingroup$ I don't understand what you mean by failure of peptide bonding between two amino acids. Do you mean post-translational cleavage into two chains like insulin? And if you want to ask a new question of whether two proteins can be translated from the same eukaryotic mRNA without any post translational modification of any sort, I can give you some examples that might surprise you. (This question has already got 4 close votes, so I imagine it will be closed soon.) $\endgroup$
    – David
    May 28 '18 at 23:17
  • $\begingroup$ 2A peptides don't cleave in the sense of proteolysis, rather, the ribosome "skips" peptide bonding and releases the current polypeptide while continuing translation of the ORF into a second polypeptide. So it's not strictly a post-translational modification. E.g. ncbi.nlm.nih.gov/pubmed/11297676 and more recently ncbi.nlm.nih.gov/pmc/articles/PMC5438344. (Note this doesn't always work, the ribosome will sometimes cancel and not translate the second polypeptide, and sometimes it won't skip and make one long fusion polypeptide) $\endgroup$
    – Armatus
    May 29 '18 at 14:01
  • $\begingroup$ My guess is there are also miRNAs that can modify what polypeptides an mRNA molecule produces; but sure, shoot :) $\endgroup$
    – Armatus
    May 29 '18 at 14:10

Answer is yes, by a logical approach, in superior organism where alternative splicing and post-transcriptional modification alter the protein structure. In bacteria, this thing is not allowed. This scenario isn't common in functional protein, and start occurring by some alteration in the splicing process.

In real life, this is nearly impossible. A protein domain could be conserved, and so different protein can share parts of the amminoacidic sequence and, by that, the mRNA. But, as far as I know, there's no study confirming the evidence of same transcript and different proteins.

  • 2
    $\begingroup$ Alternative splicing produces different mRNAs, so the first part of your answer is incorrect. You echo the poster's incorrect "post-transcriptional modification". It should be "post-translational modification", and it hardly counts as a separate protein anyway. $\endgroup$
    – David
    May 28 '18 at 14:11
  • $\begingroup$ He's not arguing about "after" or "before" splicing. So, starting from the same template, you could get different mRNA. For the 2nd sentence, you're right. $\endgroup$
    – Shred
    May 28 '18 at 15:11
  • $\begingroup$ And, just for completeness, you're saying that post-translational modification doesn't change protein structure at all. Here, you're wrong. $\endgroup$
    – Shred
    May 28 '18 at 15:12
  • $\begingroup$ Don't put words into my mouth. I know perfectly well what effects post-translational modification can have on proteins. I don't answer unclear homework questions because questions of that type should be unambiguous, and the answers often depend on the teaching context. In this case, unless it was specifically mentioned in class I would assume the reference was to a different amino acid sequence. $\endgroup$
    – David
    May 28 '18 at 15:21

Not the answer you're looking for? Browse other questions tagged or ask your own question.