The codon AGG normally codes for argine but in altered translation it codes for stop. Where does it occur?
The codon AGG normally codes for arginine in the standard genetic code, which is used by most organisms for protein synthesis. However, in some cases, the codon AGG can code for a stop signal, which means the end of translation and the release of the protein chain.
One example of altered translation where AGG codes for stop is in the vertebrate mitochondrial code, which is the genetic code found in the mitochondria of all vertebrates. The mitochondria are organelles that have their own DNA and ribosomes, and they produce proteins that are essential for cellular respiration and energy production. The mitochondrial genetic code differs from the standard code in several ways, one of which is that AGA and AGG are stop codons instead of arginine codons.
Another example of altered translation where AGG codes for stop is in some bacteria that use a variant of the standard code called the bacterial and plant plastid code. This code is used by some bacteria that live in extreme environments, such as hot springs or salt lakes, and by some plants that have plastids, which are organelles that perform photosynthesis. The bacterial and plant plastid code differs from the standard code in that UGA codes for tryptophan instead of stop, and AGA and AGG code for stop instead of arginine.
These examples show that the genetic code is not universal and can vary among different organisms or organelles. The reasons for these variations are not fully understood, but they may reflect evolutionary adaptations to different environmental conditions or functional constraints.