EasyBiologyHigh School (11–12)Heredity and Evolution › Molecular Basis of InheritanceConceptualAPA-LevelIB
The mRNA 5′-AUG GCU UUC AAA UAA-3′ is being translated…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The mRNA 5′-AUG GCU UUC AAA UAA-3′ is being translated.
- Write the anticodon of the tRNA for each of the first four codons, from its 3′ end to its 5′ end.
- Give the amino acid that each of these tRNAs carries.
- Which tRNA is the initiator tRNA?
- Which tRNA reads the codon UAA?
Need a reminder? The key ideaShow
A tRNA has an anticodon at one end and an amino acid acceptor end at the other. The ribosome reads the mRNA from 5′ to 3′, from AUG to a stop codon. A stop codon has no amino acid, so a coding region of nucleotides makes amino acids, of about 110 Da each.
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) AUG pairs with 3′-UAC-5′. GCU pairs with 3′-CGA-5′. UUC pairs with 3′-AAG-5′. AAA pairs with 3′-UUU-5′.
Step 2. (b) The amino acids are Met, Ala, Phe and Lys.
Step 3. (c) The first one, with the anticodon UAC. It reads the start codon AUG and carries methionine.
Step 4. (d) None. There is no tRNA for a stop codon. A release factor binds to UAA.
Answer: UAC, CGA, AAG, UUU; Met, Ala, Phe, Lys; the first tRNA; none.
Check. The polypeptide is Met-Ala-Phe-Lys.
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