The following base sequence is found for a mRNA fragment from wild-type E. coli:
5'- UAUCAGUAGAUAAUGUAACC-3'
1. Assuming that this sequence corresponds to the middle of a gene's coding region, give the amino acid sequence of the protein you would expect the fragment to encode.
Write your answer in the (lower case) 3 letter amino acid code such as leu, trp, phe, etc, and place a comma after each amino acid and no spaces or periods: example: met, phe, trp, arg, asp

The correct answer is:  (leu/ile/val), ser, val, asp, asn, val, thr.

Explanation:

In the question, a mRNA (messenger Ribonucleic acid) sequence is given in the 5'→3' orientation.The Ribosome is responsible for translating the ribo-nucleotide code (mRNA) into the amino acid code (polypeptide).The Ribosome reads the ribo-nucleotide codes in form of triplets. This means that three ribo-nucleotides code for a single amino acid. Each such triplet is called a Codon. Hence, each codon codes for a single amino acid.The specific amino acid that a codon is specific for, is given by the Genetic Code table.Dividing the given sequence into codons and representing the amino acids encoded below:

                         5'- UAU  CAG  UAG AUA  AUG  UAA CC-3'

                                tyr      gln    stop

The above codon frame is not possible because UAG is a stop codon, where translation ends and that happens only at the end of the mRNA at not in between. The question states that the sequence is taken from the middle of the gene's coding region.So changing the frame of the codons,

                5'- UA            UCA     GUA    GAU    AAU     GUA     ACC-3'

                         ↓             ser         val       asp      asn       val       thr

                (leu/ile/val)

In the first codon the first nucleotide is missing, so the exact amino acid encoded cannot be determined. However, as the rest two nucleotides are given, it can be predicted that the amino acid can be: leu, if the first nucleotide is U or C. ile, if the first nucleotide is A. val, if the first nucleotide is G.The amino acid sequence would be:  

                                (leu/ile/val), ser, val, asp, asn, val, thr

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