|
Title: Hypothetical strain of E. coli Post by: msitaly83 on Oct 31, 2010 Consider a hypothetical strain of E. coli that is isolated from individuals who are suffering from a severe gastrointestinal illness. Analysis of its sequenced genome reveals a region approximately 80 kilobase pairs in length that is not present in laboratory stains of E. coli. Furthermore, analysis of the open reading frames (ORFs) in this region reveals significant differences in codon usage compared to the ORFs in rest of the genome. What do these observations suggest about this region of DNA, and the mechanism(s) by which it was incorporated into the genome of this strain of E. coli?
Title: Re: Hypothetical strain of E. coli Post by: bio_man on Oct 31, 2010 An open reading frame is a DNA sequence that contains a start codon and a stop codon in the same reading frame. In a gene, ORFs are located between the start-code sequence (initiation codon) and the stop-code sequence (termination codon). ORFs are usually encountered when shifting through pieces of DNA while trying to locate a gene. The existence of an ORF, especially a long one, is usually a good indication of the presence of a gene in the surrounding sequence. My guess is, a coliphage (bacteriophage) must have infected the E. coli that was isolated from the gut with a specific gene within a pre-existing ORF - however, I'm not totally sure :-\.
|