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Hi guys ,, these are two questions in Kaplan LN 2012 genetics and biochem in chapter 4 ,, which I think there is some sort of mistake in it !
Q-2 page 67
ATGCAA > ATG(T)AA
what kind of mutation is this ??
The answer is : nonsense mutation because the sequence now contains TAA which will be transcribed to UAA in the mRNA ...
My comment : when TAA is transcribed to mRNA it will be UUA ,, not UAA as it appears in the explanation !! what do u think guys , Or I understood it wrong ?
the other question
Q11 page 70
Normal Gene ATC ATC TTT GGT
Mutant Gene ATC AT* **T GGT
What will be the effect on the amino acid sequence ??
the answer in the explanation is based upon that ATC will be transcribed as AUC .. is this right ??
Regarding the question on page 67, the sequence given is that of a coding strand, so the mRNA that will be transcribed is gonna be identical to it with the sub. of T-U. This is not a template strand in which you have to come up with a complementary sequence. So I do think that their answer is correct.
Your second question (pg. 70) is not very clear. But here's my understanding of what they're asking in the question: They wanna know what gene is lost and in this case its TTT (The 3rd base deletion in ATC doesn't make a big difference as the third base isn't specific anyways, so therefore, AT=phenylalanine), whereas the mutation is more dramatic in the case of **T because now you've completely deleted the amino acid. There is no change in C-terminal sequence because you're deleting 3 bases.
I hope this helps!
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