Question

The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is True

a) All organisms use the same start codon.
b) Some organisms use different codons for the same amino acid.
c) The code is identical in all kingdoms of life.
d) The code is entirely based on non-overlapping triplets.

Answer 1

The existence of exceptions to the universal genetic code is evidenced by some organisms using different codons for the same amino acids, as seen with the codons UGA and UAG for selenocysteine and pyrrolysine, respectively.

Step-by-step explanation:

The evidence that the "universal" genetic code has exceptions can be found if b) some organisms use different codons for the same amino acids, is true. While the genetic code is nearly universal, reflecting a common evolutionary origin for all life, certain organisms have evolved to use alternative codons for the same amino acids. An example of this is the use of the codon UGA, which typically signals a stop command in protein synthesis but in some organisms, it codes for the amino acid selenocysteine. Moreover, pyrrolysine is another unusual amino acid encoded by certain archaea and bacteria, which uses the UAG stop codon. The existence of these exceptional cases illustrates the slight variations in the universal genetic code across different life forms.