Will all organisms with the same 3 nucleotide sequence in the codon produce the same exact same amino acid. I read that the three nucleotide sequence will code for a particular amino acid. I did not understand if that is the case across organisms. Can someone explain this in simple terms.
Although the answer to this question may be found in Mitochondrial Genetic code, because that answer is primarily about mitochondrial genetic codes, I shall give a more directed answer here.
Because the same genetic code that was elucidated in bacteria was found to apply to higher eukaryotes, it was initially assumed that the genetic code was universal, and was referred to as such. Subsequently it was discovered that mitochondria did not generally employ this ‘universal’ code, which is now usually referred to as the ‘standard’ code — indeed different mitochondrial codes were found in different organisms.
However the question seems to be more concerned with the genetic codes of bacteria and the nuclear genetic codes of eukaryotes. Here also there are deviations from the standard genetic code, which can be found listed either on this Wikipedia page or at NCBI.
Below are some examples from the NCBI list (where references may be found) with the standard coding in parentheses:
Mycoplasma UGA Trp (Ter) Ciliates, Dasycladacean and Hexamita UAA Gln (Ter) UAG Gln (Ter) Euplotidae UGA Cys (Ter) Candidate Division SR1, Gracilibacteria UGA Gly (Ter) Pachysolen tannophilus CUG Ala (Leu)