Nonsense mutation and suppression. Schematic animation showing the process by which a nonsense mutation of genetic material can arise, and how it is suppressed. The animation starts at upper left with a sequence of tRNA (transfer ribonucleic acid) bound to a sequence of mRNA (messenger ribonucleic acid). The RNA nucleotide bases are represented by letters: adenine (A), cytosine (C), guanine (G), and uracil (U). The tRNA (AUG) is carrying an amino acid (green, Met - methionine). The mutation (red) occurs in the mRNA, where the cytosine (C) nucleotide base turns into guanine (G) at lower left. This is known as a premature stop codon, or a nonsense codon. The animation continues at upper right, with another amino acid (green, Tyr, tyrosine) bound to the same sequence of tRNA. This time, the tRNA mutates (G turns to C) to produce what is known as a nonsense suppressor. The final stage of the animation shows this tRNA mutation moving across to bind to the mRNA nonsense codon. The nonsense suppressor reads the stop codon as if it was a normal codon, and this allows the RNA transcription to continue as normal, despite the mutation. For this animation with labels, see K004/2014. |