Question

Below is a mature eukaryotic mRNA transcript. Translate this mRNA into a protein, also showing the tRNA anticodons involved. Make sure you start and end translation in the right place! Label the ends of the polypeptide chain as N and C terminus.
mRNA: 5'GMUUACAUGCGGCUCAGUUGAGGCGAAAAAA 3'
tRNA:
amino acids:

Answer 1

Answer:

mRNA ⇒ 5'GMU  UAC  AUG  CGG  CUC  AGU  UGA  GGC  GAA  AAA  A 3'

tRNA ⇒                           UAC  GCC  GAG  UCA  ACU

protein ⇒ N - MET   ARG   LEU   SER   Stop - C

Explanation:

In protein synthesis, the ribosome reads mRNA in the 5´ to 3´ direction, and, according to the codons that are being readen, tRNA transfers the correct amino acids to build the polypeptide chain. A codon is a short sequence of three nucleotides that store the genetic information for the aminoacids´ assembly. Each tRNA has two important sites. One of them that couples with the codon of the mRNA molecule, named anticodon. The other site couples with an amino acid. tRNA allows amino acids to align according to the nucleotidic sequence in the mRNA molecule.  

Once the new amino acid links to the growing peptidic chain, the binding between the amino acid and the tRNA molecule breaks. The tRNA is now free to join another amino acid and repeat the cycle.  

The protein is synthesized from the amino terminus to the carboxy terminus, while the added amino acids to the chain are coded by a codon formed by three bases in the mRNA. mARNs also have a start and end codon that are the signals of the synthesis initiation and finish. When the ribosome reaches the end codon, protein synthesis is over.    

Each of the codons represents one of the 20 amino acids used to build the protein. Each amino acid can be codified by more than one codon. From the total 64 codons, 61 codify amino acids, and one of them is a start codon. The left three codons are stopping translation points.

The codons indicating the initiation or stop points during the translation process are:

• The start codon AUG is the most common sequence used by eukaryotic cells and places near the 5´extreme of the molecule.  

• The end codons are UAA, UAG, UGA.

Protein synthesis initiates in the AUG start codon -Metionin-, and ends when reaching either of the stop codons UAA, UAG, UGA.

In the exposed example we have the following mRNA.

mRNA ⇒ 5'GMU  UAC  AUG  CGG  CUC  AGU  UGA  GGC  GAA  AAA  A 3'

Codons are separated by a space left between them. AUG is the start codon placed near the 5´ extreme. UGA is the end codon near the 3´ extreme. tRNA will add amino acids from the start codon, not before.

tRNA ⇒ UAC  GCC  GAG  UCA  ACU

Anticodons are separated by a space left between them.

protein ⇒ N - MET   ARG   LEU   SER   Stop - C

Each mRNA codon codifies for an amino acid. The start codon codifies for methionine. AUG = Met, CGG = Arg, CUC = Leu, AGU = Ser, UGA = Stop codon. The amino terminus is represented as an N and the carboxy terminus is a C. The first extreme to be translated carries the amino-terminal group, while the other extreme carries the carboxy-terminus group.