Imagine discovering a loss-of-function mutation in a eukaryotic gene. You determine the gene's nucleotide sequence from the start site for transcription to the termination point of transcription and find no differences from the wild-type sequence. Explain where you think the mutation might be and how the mutation might be acting.

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Hi everyone. Let's look at the next question. It says a null allele is a non functional caused by a genetic mutation. If the transcript OEMs of the wild type and mutant are identical, where did the mutation most likely have an impact? So we're talking about an issue where a mutation is causing a little that produces a gene that is non functional. The protein is nonfunctional. So where do the motivation of an impact? If the transcript tones of the wild type and mutant are identical, all transcriptome, as you might guess by the name. Since transcription is that process of DNA to RNA is the total of all M. R. N. A. For the cell. So if the transcript tones are identical, therefore we know that the mutation was not in the D. N. A. Not in the genes themselves and didn't affect transcription. And if the messenger RNA for both the wild type and mutant is identical then it's not going to have an impact in the translation process as a translation is when that M. R. N. A. Is used to make a protein but the M RNA is identical between the wild type and mutant. So where is the only place left for to have an impact? And that would be in post translational modification when the protein is modified after translation. Examples of this include phosphor relation of the protein addition of phosphate groups? Mhm. And methylation addition of methyl groups. So again, if the messenger RNA is identical between wild type and mutant, then the place where we see the mutation having impact must be in the post translational part of the process. So let's look through our answer choices choice A says during DNA synthesis. Well this is not correct again, since the M RNA is identical to the genes it was transcribed from can't have had the mutation affecting them. So that would not be our answer choice B says during the transcription process. Well, again, the transcript dome is the result of the transcription process and the transcription is identical. So this is not where we have the impact choice C. Says during the genetic exchange of parental genes. Again, if there were an issue, if you saw the mutation at the gene level, you wouldn't see identical transcript ums in the mutant and wild type. So Choice C. Is not an answer. We've got choice D during the post translational stage. And as we talked about that is the likely impact here since the transcriptions are identical. So where is that mutation? Most likely have an impact that the transcriptions of wild and mutant are identical. Choice D during the post translation stage. And this makes sense. Since we say No Alley is a non functional Alley and we expect to see functional effects when we look at proteins in the cell since the proteins that carry out those functions. See you in the next video

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Key Concepts

Loss-of-Function Mutation

Gene Regulation

Transcription and Translation