A full-length eukaryotic gene is inserted into a bacterial chromosome. The gene contains a complete promoter sequence and a functional polyadenylation sequence, and it has wild-type nucleotides throughout the transcribed region. However, the gene fails to produce a functional protein. List at least three possible reasons why this eukaryotic gene is not expressed in bacteria.

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Hi, everyone. Welcome back. Let's look at our next question. Which of the following is a possible explanation of a eucaryotic gene which fails to produce a functional protein when incorporated into a bacterial chromosome. And our answer choices are a in bacteria. The codons may encode for different amino acids than in new car outs. Choice B, the U Caro gene may contain enrons which are non coding regions of DNA but interrupt the coding sequence. While bacteria do not have the machinery to process en enrons. Choice C, the U Caro gene may require posttranslational modifications such as glycosylated or phosphorylation that cannot be performed by bacterial enzymes. Choice D the gene may be regulated by eucaryotic specific transcription factors or regulatory elements that are not present in bacteria. Choice. E all of the above or choice F none, none of the above. So let's think through this scenario. Keeping in mind those last two choices, all of these may be correct or perhaps none of them are. So when we try and express a U Caro gene in a bacterial cell, we have to account for the differences between U carats and pro carry outs when it comes to gene expression. So let's go through these answer choices and see which might explain differences that might result in a nonfunctional protein in this scenario. So choice a says that you might have coons encoding for different amino acids in bacteria. Well, this is indeed a possibility, the genetic code is mostly similar, but there are differences between e carats and pro carats and there are some codons that are different between the two. So if that happens to be an important amino acid and the codon codes for something different, you might end up having a non functional protein by a key change in an amino acid. So choice a definitely a possibility. It um definitely would describe a reason why you'd have a nonfunctional protein. Since we have our answer. Choice of all of the above. I'm not going to choose it as my answer, but I'll mark it with a dot To indicate that's a correct answer. So I'm going to go ahead and eliminate the choice F none of the above since I've already got one correct answer. Let's look at choice B now it says that the eukaryotic gene might contain enrons. Well, that would be an issue for a bacterial cell because while enrons are spliced out of M R N A in eukaryotic cells, bacteria don't have enrons in their genes. So an Enron might interrupt the coding sequence of this gene resulting in a nonfunctional protein. So choice B also a reason why you might have that nonfunctional protein. So put another dot There, well, if I'm on a test, so I want to get through these questions without taking a long time. I already have two correct answers. So I'm going to select choice E all of the above as my answer. Once I have more than one correct answer, I know that's, I want to go with all of the above, but here I want a thorough explanation. So we'll go ahead and look at choices C and D. So I see the UK Caro gene might require posttranslational modifications. Well, yes, this would be another reason why you might end up with a nonfunctional protein. Eukaryotic cells do add these posttranslational modifications to the protein. Things like as our quest choice says, glycosylated phosphorylation, addition of small sugar groups, phosphate groups and those can't be done. And in bacteria, the bacteria don't have the enzymes to perform those reactions. So if those are necessary modifications to have a functional protein, that would be a reason why you wouldn't see that able to happen in a bacterial cell. So choice C also correct as we'd expect. And then finally, choice d the gene may be regulated by e Caro specific transcription factors or regulatory elements not present in bacteria. So choice C dealt with modifications after we've uh translated our R N A into protein. In this case, it's before it's even transcribed, there are transcription factors there are regulatory elements that govern the transcription of R N A and some of these might be eukaryotic specific in which case that couldn't take place in bacteria. So choice D also one of our reasons. So what are possible explanations for a eukaryotic gene that can't produce a functional protein in a bacterial cell? Choice? E all of the above. See you in the next video.

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Key Concepts

Promoter Compatibility

Post-Transcriptional Modifications

Codon Usage Bias