An mRNA reads 5′-GCAUGUUCGGAAGUUGAUCC-3′…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
An mRNA reads 5′-GCAUGUUCGGAAGUUGAUCC-3′. Use the table of the genetic code.
- At which base does the first AUG begin? Count from the 5′ end.
- Write the polypeptide that is made, in three-letter names.
- How many amino acids does it have?
Need a reminder? The key ideaShow
A codon has three bases. Of the 64 codons, 61 code for amino acids and 3 are stop codons, and AUG is the start codon. A point mutation can be silent, missense or nonsense. An insertion or a deletion of 1 or 2 bases shifts the reading frame, and an insertion or a deletion of 3 bases keeps it.
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.
Given. 5′-GCAUGUUCGGAAGUUGAUCC-3′.
Plan. Find the first AUG, then read the codons one after another.
Step 1. (a) G is base 1, C is base 2, and A is base 3. The first AUG begins at base number 3.
Step 2. (b) The codons are AUG, UUC, GGA, AGU and UGA. These code for Met, Phe, Gly, Ser, and Stop. The polypeptide is Met-Phe-Gly-Ser.
Step 3. (c) The stop codon carries no amino acid, so the polypeptide has amino acids.
Answer: base ; Met-Phe-Gly-Ser; .
Check. The bases after the stop codon, CC, are not read.
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