Question

Complete the following vocabulary exercise related to the process of translation of mRNA to protein by the ribosome. Match the words with the appropriate blank in the sentences.

Words: tRNA, aminoacyl-tRNA synthetase, translation, initiation, termination
Sentences:
1. ______ of translation happens when the ribosome hits a stop codon on the mRNA.
2. The process, performed by the ribosome, of reading mRNA and synthesizing a protein is called _______.
3. Amino acids are attached to tRNA by enzyes called ______.
4. The RNA that has an amino acid attached to it, and that binds to the codon on the mRNA, is called a _______.
5. __________ of translation always happens at the start codon of the mRNA.

Answer 1

The answers;

1. Termination. Out of the 64 codons, UAG, UAA, and UGA are the stop codons that terminate translation when encountered by the ribosome. These three do not code for any amino acid but rather cause the translation complex to dislocate.

2. Translation. In this process, the ribosome ‘reads’ the codon and brings in a t-RNA with an anticodon to the codon. This tRNA carries a specific amino acid (for that codon) and engages in the P-site of the ribosome. The amino acid is taken from the t-RNA and used to elongate the polypeptide chain being formed. Thereafter the empty t-RNA dislocates.

3. Aminoacyl-tRNA synthetase. When a tRNA brings in an amino acid to the initiation complex, it is dislocated when ‘empty’. Aminoacyl-tRNA synthetase then catalyzes the reattachment of another amino acid through a chemical reaction called esterification. The cognate tRNA then become an aminoacyl-tRNA.

4. tRNA . Every tRNA has an amino acid attached to it. The type of amino acid (out of the 22 amino acids) is determined by the anticodon on the tRNA. There are many codons that are amino acids meaning that there are redundant codons that specify for the same amino acid.

5. Initiation. Initiation begins by the formation of an initiation complex. This complex is comprosed by the two subunits of the ribosome, and the mRNA. The complex becomes compelete when a Met-tRNA (a tRNA with a methionine amino acid) engages the P-site and then translation begins.