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 a simple Q but has confused me a lot!!!  




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Author4 Posts
  #1

a 4yr old toddler with cystic fibrosis is seen by his physician for an upper respiratory infection with pseudomonas aeruginosa. He is started on oral norfloxacin and referred to a CF center as a potential candidate for gene therapy. Prior genetic testing of the pt identified the mutation causing CF as a 3 base pair deletion in exon 10 of the CF gene. The nucleotide sequences of codons 506-511 in this region of the normal and mutant alleles are compared below
506 507 508 509 510 511
normal gene ATC ATC TTT GGT GTT TCC

mutant gene ATC AT- --T GGT GTT TCC

a) deletion of phenylalanine residue with no change in C-terminal sequence
b)deletion of a leucine residue causing a change in the C-terminal sequence
c) deletion of a phenylalanine residue causng a change in C-terminal sequence
d) deletion of leucine residue causing no change in the C-terminal sequence

pls refer to the genetic code table which shows the codes for aminoacids in your respective notes as I do not know how to put that table in here and typing that out will eat up a lot time.
I now confused that that table which states all the codons for specific aminoacids ..whether those are codons or anticodons and like mRNA which has U for T ...does tRNA also has U for T ???
would be of great help if someone tried to explain me abt these things
thank you





  #2

yea tRNA does....all RNA(rRNa,tRNA,mRNA) have U instead of T
the genetic code shows codons....codons are on the mRNA...the anticodon is on the tRNA.

whts the answer to this Q? A?
i am guessing u dont need to refer the genetic code for such Qs....rather most if not all teh Qs in teh USMLE.....u shd know tht CF is assoc w/ a deletion of the amino acid Phe. Tht rules out choice B and D. Also since the deletion is smack right in the middle...i think neither C nor N-terminus is involved........or iam totally off!


  #3

you are very much correctsmiling face the ans here is A...thank you so much looks like its high time for me to use some of my brains toosmiling face


  #4

A-





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