Question

If molecules of mRNA have the following nucleotide base sequences, what will be the sequence of amino acids in polypeptides synthesized by eukaryotic ribosomes? Remember, transcription starts with an AUG codon. 1. 5′–AUGGGGAUACGCUACCCC–3′ 2. 5′–CCGUACAUGCUAAUCCCU–3′ 3. 5′–CCGAUGUAACCUCGAUCC–3′ 4. 5′–AUGCGGUCAGCCCCGUGA–3′

Answer 1

The mRNA is used to synthesize polypeptides in a process called translation, and for that the mRNA is interpreted as a series of groups with three nucleotides each, called codons. So for each three letters, we have a codon. The codons transcribe the following amino acids: Alanine, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Proline, Serine, Threonine, Tryptophan, Tyrosine, Valine, Selenocysteine.

The codons are organized in a chart, as the one that follows:

As the translation starts with an AUG codon, we sometimes have to leave some trios behind. The answer would be as follows:

1. AUG - met | GGG - gly | AUA - ile | CGC - arg | UAC - tyr | CCC - pro

The sequence would be MET-GLY-ILE-ARG-TYR-PRO

2. We will start only after the AUG codon

AUG - met | CUA - leu | AUC - ile | CCU - pro

The sequence would be MET-LEU-ILE-PRO

3. Again, we start after the AUG codon, and if the stop codon shows up the translation stops

The sequence would be only AUG - met | UAA - stop

MET

4. AUG - met | CGG - arg | UCA - ser | GCC - ala | CCG - pro | UGA - stop

The sequence would be MET-ARG-SER-ALA-PRO