Yes,this hypothesis of Beadle and Tatumn is very old now it comes as one gene many proteins/polypeptide.Simply as in case of human genome there are around 26,000-30,000 genes and protein around 90,000 or 1,00000.Although before Human genome draft it was hypothesized equal no of proteins.

It comes under regulation or control of Alternative Splicing where one gene can give its various transcripts and ultimately various proteins.For details please read "Alternative Splicing" one important paper of "ALTERNATIVE GENOME-by Altman.

Best Wishes

Which phage? Some viruses produce one long pre-protein - then use proteases to cut it up & the different bits have different functions.

yes i do agree to Micheal sir, please specify the phage in the query.......Several phases have the quality to transcribe and translate long sequence of protein, then further digests it to get multiple small segments of proteins and these multiple proteins shows different functions, Here one gene one protein function is valid but confusion arises because of the strategy of Transcription and Translation approached by the phage type.......GDLK

I think that there is overlapping of genes.

I think that there is overlapping of genes

Viruses as a whole, not just phages, go around expressing their genomes in very different ways. The main issue with them is that several proteins are coded for by a genome that is not sufficiently large, and may either be RNA or DNA. Also, many viral ORFs/genes are arranged in continuation, and hence there are several start/stop codons. This feature makes their translatable phases akin to a polycistronic mRNA, while in eukaryotes, monocistronic mRNAs are generally translated. Viruses hence have evolved various strategies to overcome this, and other such handicaps, e.g. readthrough protein, subgenomic RNAs, internal ribosome entry points etc. Of course, many of these would not apply to bacteriophages since they infect bacteria and not eukaryotes. In this gamut of strategies, one is differential splicing, where a single mRNA which is the product of a single gene, is cut and joined, i.e. differentially spliced, at different locations, thereby yielding different translatable mRNAs that would yield different proteins. This also falls within the realm of resource conservation. One of the other ways, referred to in a reply above, is the translation of a single polyprotein, that is later cleaved into individual functional proteins, each of which is different from the other.

As Mahmood said we can add to Vivek answer something that I think is unique to viruses. generally we are used that the gene transcription has a one to one correspondence and it might have some alternative splicing. This is also valid for viruses with a mention that here sometimes you can have a gene that when fully expressed will produce a protein and when only partially expressed will produce another protein (overlapping ORFs). Also there is something that I think is only specific to viruses : you can have an ORF expressing a gene in one sense and an overlapping ORF running in the opposite direction.

Yes, Vlad, that is right. In my earlier reply, I have referred to only four, but there are actually over a dozen strategies by which viral genomes are expressed, and the one you mention is one such.

thanks all for ur valuable answer..most of u r saying that one gene may express protein or polypeptide of different type...then how in case of T7 phage cDNA library it express 10 copies of each protein against cDNA or in case of M13 phage ,it express 2700 copies P VIII coat protein? waiting for ur kind reply...............