MOL - Translation [LESSON]

Translation

Translation is the assembling of protein molecules from information encoded in mRNA. There are multiple types of RNA involved:

  • Messenger RNA (mRNA) - A single strand of nucleotides that transcribes information from DNA to the cytoplasm for translation. A sequence of three bases in an mRNA strand that codes for one amino acid is called a codon.
  • Transfer RNA (tRNA) - A single folded strand that carries a specific amino acid to the site of protein synthesis. A sequence of three bases on one end of a tRNA molecule is called an anti-codon.
  • Ribosomal RNA (rRNA) - A globular form of RNA and protein that are the major constituents of ribosomes. Ribosomes include E, P, and A binding sites for translation initiation, elongation, and termination.

After the mRNA has been transported from the nucleus  to the cytoplasm, ribosomes bind to the mRNA and begin the translation process. To convert the mRNA into protein, tRNA is used to read the mRNA sequence within the ribosome to create the correct sequence of amino acids. The sequence of amino acids is critical to the performance of the protein; even a single amino acid in the wrong place can cause a disease.

The ribosome starts at the codon AUG. Each tRNA brings the right amino acid matching the sequence of codons.

The mRNA is translated in codons, a sequence of three nucleotides. The tRNA molecule contains a set of three nucleotides that complement a codon, called an anticodon, at one end and a site for a specific amino acid on the opposite end. Translation begins at a specific coding sequence on the mRNA strand referred to as the start codon and ends at another coding sequence referred to as the stop codon. As the anticodons match up with complementary codons in the ribosome, amino acids on each tRNA are joined together by peptide bonds to form a polypeptide chain. When the stop codon is reached, translation stops, and the mRNA leaves the ribosome. The polypeptide chain folds into its specific shape and is processed and packaged for use. Here is a great animation of translation:

Watch the Translation video below for more details about translation.

Sequence the steps of translation below after watching the Sequence Translation video.

Practice using the codon chart below to look up the correct amino acid brought in by each corresponding segment of mRNA.

The image shows each codon and the corresponding amino acid.

Now you try to create the correct mRNA and then amino acid:

What would the correct mRNA sequence be for this DNA? AGTACCTTAAGTAGTGGCCTTCATTAATC

UCAUGGAAUUCAUCACCGGAAGUAAUUAG

 

What would the correct protein sequence be for this mRNA (remember to start at the start codon)? UC AUG GAA UUC AUC ACC GGA AGU AAU UAG

Met – Glu – Phe – Ile – Thr – Gly – Ser – Asn - Stop

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