Question

Below is the sequence from the 3' end of an mRNA.

5'-.........CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3'
If you were told that this sequence contains the stop codon for the protein encoded by this mRNA, what is the anticodon on the tRNA in the P site of the ribosome when release factor binds to the A site?
(a) 5'-CCA-3
(b) 5'-CCG-3'
(c) 5-UGG-3
(d) 5'-UUA-3'

Answer 1

The correct answer is a) 5′-CCA-3′.

Step-by-step explanation:

It is given that in the given mRNA sequence there is a stop codon for the protein it forms, the sequence from the 3' end of mRNA is -

5'-.....CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3'

Making triplet codes from 3' end -

5'-....CC GUU ACC AGG CCU CAU UAU UGG UAA CGG AAA AAA AAA AAA AAA-3'

In this UAA is the stop codon and 5'-UGG-3' is the codon adjacent to stop codon UAA in the mRNA sequence which will be present at P-site in the mRNA sequence so the anticodon will be the corresponding anticodon for 5'-UGG-3' is 3'-ACC-5' or simply 5'-CCA-3'.