[khanar]

USMLEWorld is saying that the cause of the phenylalanine deletion in cystic fibrosis is due to frame-shift mutation and not due to mis-sense mutation as I answered the question wrongly.
Their explanation is not convincing and perhaps is wrong.
Can anybody please help me with this issue preferrably with referencing.

Thanks

 

[khanar]

In-Frame Vz Frame-shift mutations

I would assume the deletion of the protein at the 508 position is due to frame shift deletion as this leads to a loss of 3 bases from the sequence of amino acids. As for the missense mutation, that would mean a single base substitution leading to a change in that particular amino acid alone and does not effect the remainder of the reading frame. I hope this helps! For references, see if you can find lippincott for biochemistry (i heard its a great book).

Frame-shift mutation means deletion or addition of any number of bases but not multiples of three. Loss or gain of 3,6,9, ...etc bases is called In-Frame mutation.

 

[khanar]

That UW question is wrong, send them feedback
Delta F508 is a deletion of phenylanaline amino acid from the CFTR gene. Which as Sarah said, this is called In-Frame mutation not frame-shift mutation.
See this reference where it explains that in details

The link to that page is here
http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/cftr.shtml

Mis-sense mutation does not result in amino acid deletion but rather amino acid substitution (such as the case in Sickle cell bete globulin gene).

 

[khanar]

I agree with YoramFishke but I want to add that cases of CF are not all due to the 508 mutation there 100 of other mutations and they can be frame-shift so double check the UW may be they did not specify 508

 

[HouseWannabe]

From what i read, a frameshift mutation, is any mutation that shifts the reading frame. So in this case, if the entire Phe codon is deleted that would still result in a shift of the reading frame....