Question

1. A codon is a series of three bases in mRNA which is equivalent to the 3 bases in DNA; this triplet code corresponds to one amino acid. Once the mRNA is attached to a ribosome, it can assemble the protein by translating from the “language” of nucleic acids to the “language” of amino acids. What is the processed called?

2. In order to synthesize a protein molecule, amino acids need to be aligned in the proper sequence along the RNA sequence. tRNA molecules are responsible for aligning amino acids along the mRNA sequence in the ribosome. The shape of the tRNA molecule looks like a four-leaf clover. An amino acid is attached at one end of the tRNA and an anticodon sequence is found at the other end of the tRNA. The anticodon sequnce helps the tRNA bind to the mRNA molecule. See the slides and Fig. 4.24 and Fig. 4.25 for help.

3. This process of tRNAs binding to the mRNA, peptide bonds being formed between amino acids, tRNAs being released, and ribosome moving along the mRNA sequence repeats until the ribosome encounters a STOP codon in the mRNA sequence. What does this signify and what event occurs?

Answer 1

1. Translation = mRNA -----> Protein
It involves the conversion of 'language of nucleic acids' to the 'language of amino acids' with the help of tRNA and ribosomes.
The tRNA brings amino acids to the translating ribosome.
The ribosome forms the peptide bond between amino acids.

2. When the ribosome encounters a stop codon (UGA, UAA, or UAG) in the A-site, the translation is terminated.
This is due to the fact that there is no corresponding tRNA that can recognize these stop codons.
Translation termination si followed by release of the nascent polypeptide and dissociation of the ribosomal subunits.