Part of the genetic code is given. AAA and AAG: lysine (Lys)…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Part of the genetic code is given.
- AAA and AAG: lysine (Lys).
- AAU: asparagine (Asn).
- UUU: phenylalanine (Phe). CUU: leucine (Leu).
- UGG: tryptophan (Trp).
- UAA and UGA: stop.
Name each change as silent, missense or nonsense.
- AAA changes to AAG.
- AAA changes to AAU.
- UGG changes to UGA.
- UUU changes to CUU.
Need a reminder? The key ideaShow
A codon has 3 bases, and each base can change to any of 3 others, so one codon has 9 possible substitutions. A change is silent if the amino acid stays the same, missense if it changes, and nonsense if the new codon is a stop codon. The insertion or the deletion of a number of bases that is not a multiple of 3 shifts the reading frame.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) AAA and AAG both stand for lysine. The change is silent.
Step 2. (b) AAA is lysine and AAU is asparagine. The amino acid changes, so the change is missense.
Step 3. (c) UGA is a stop codon. The change is nonsense. The protein ends early, at the position of tryptophan.
Step 4. (d) UUU is phenylalanine and CUU is leucine. The change is missense.
Answer: (a) silent; (b) missense; (c) nonsense; (d) missense.
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