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Imagine a gene with $n$ exons and $m$ introns. How many proteins are possible from that gene? Would all the proteins be isoforms?

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closed as unclear what you're asking by terdon, WYSIWYG, Rover Eye, dustin, canadianer May 2 '15 at 15:53

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Is this a homework question or a assignment? If so, please tag it accordingly and tell us what you have done to solve this. $\endgroup$ – Chris May 2 '15 at 8:01
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    $\begingroup$ This question cannot be answered in its current form. How many of the exons contain a valid START codon? How many exons are in UTRs? How many actually code for protein and don't contain in-frame STOP codons? Please edit and make it more specific. $\endgroup$ – terdon May 2 '15 at 9:09
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I might be wrong, but aren't numbers $n$ and $m$ are connected as $n=m+1$?

Answer seems to be combinatorial: how many combinations of $n$ objects can be assembled under certain restrictions? Namely, how many isoforms certain gene can have.

Restrictions include: how many exon-intron junctions on codon (or precisely between codons), how many exons are actually contain protein-coding sequence of mRNA (some exons are coding untranslated region, 3'- or 5'-UTR, for example), how certain gene processes alternative splicing.

So, as you can see, answer will highly depend on sequence of given gene. As far as I know, maximum number of isoforms is limited by 5, even though there are genes with hundreds of exons.

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