Coding Region: Introns and Exons (EK FL 1: #159)

[banana_phone]

So...I took EK FL 1 and am doing my post-game analysis. There is a discrete which states:

Beta-thallasemia is a genetic disorder characterized by decreased levels of a functional beta chain in hemoglobin. This disorder is caused by a single nucleotide change in a coding portion of the gene that is not included in the mature mRNA transcript. How is this possible?

B) Point mutations in exons changing the final structure so beta chain is nonfunctional
C) Point mutations in introns causing incorrect splicing and nonfunctional beta chain

Now, I was a TA for a Genetics course. I was under the impression that introns are NOT CODING but I also know that they aren't included in the final transcript. The answer is C, and their justification states that the intron mutation is the only mutation in a coding sequence that wouldn't be in mRNA transcript.

Are introns considered coding sequences? Have I been wrong about this for 3 years? Or is just a bad explanation/wording of the question....obviously exons are in the mature transcript, so maybe this is just a case of BEST answer vs RIGHT answer?

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[bee17]

I think you are correct, and EK worded the problem incorrectly. A mutation in an intron would be in the open reading frame, but not in the coding sequence.

 

[yeasureyoubetcha]

Beta-thallasemia is a genetic disorder characterized by decreased levels of a functional beta chain in hemoglobin. This disorder is caused by a single nucleotide change in a coding portion of the gene that is not included in the mature mRNA transcript. How is this possible?

B) Point mutations in exons changing the final structure so beta chain is nonfunctional
C) Point mutations in introns causing incorrect splicing and nonfunctional beta chain

Now, I was a TA for a Genetics course. I was under the impression that introns are NOT CODING but I also know that they aren't included in the final transcript. The answer is C, and their justification states that the intron mutation is the only mutation in a coding sequence that wouldn't be in mRNA transcript.

Are introns considered coding sequences? Have I been wrong about this for 3 years? Or is just a bad explanation/wording of the question....obviously exons are in the mature transcript, so maybe this is just a case of BEST answer vs RIGHT answer?

Point mutation at the exon-intron boundary/recognition site could cause the intron to be left in and truncation of the protein when the ribosome runs over a stop in the intron. That would be my guess.

 

[aldol16]

Now, I was a TA for a Genetics course. I was under the impression that introns are NOT CODING but I also know that they aren't included in the final transcript. The answer is C, and their justification states that the intron mutation is the only mutation in a coding sequence that wouldn't be in mRNA transcript.

By definition, an intron is non-coding. However, this doesn't change the right answer. It's still C.

 

[yeasureyoubetcha]

By definition, an intron is non-coding. However, this doesn't change the right answer. It's still C.

Actually there have been regulatory RNAs found to be coded within introns. They usually have some sort of regulatory capacity of the gene they are within or related genes. What is meant is non-protein coding I think. I believe its still a new area of study. Still a lot of unknowns

 

[aldol16]

Actually there have been regulatory RNAs found to be coded within introns. They usually have some sort of regulatory capacity of the gene they are within or related genes. What is meant is non-protein coding I think. I believe its still a new area of study. Still a lot of unknowns

Well, it is generally accepted that "coding" refers to the "coding" of proteins, as in "genetic code."

 

[yeasureyoubetcha]

Well, it is generally accepted that "coding" refers to the "coding" of proteins, as in "genetic code."

True. What we know keeps changing. Check out the ENCODE project. Some pretty interesting stuff

 

[aldol16]

True. What we know keeps changing. Check out the ENCODE project. Some pretty interesting stuff

Yeah, I keep up with recent happenings in the fields I'm interested in and there are actually a lot of interesting things going on in engineering proteins (think: doing reactions that nature cannot do) and also designing novel catalysts for feedstock conversion. I'm not so interested in genomics because I see less potential there, but I'm sure there are a lot of interesting things going on in all fields of science (revision of the Standard Model for one).