Mitochondrial and chloroplast codes: In some eukaryotic organelles, how does the genetic code compare to the standard bacterial code?

Introduction / Context:The genetic code is nearly universal, but notable exceptions occur in organelles such as mitochondria (and some chloroplasts). Recognizing these deviations is important in genomics and interpreting organelle-encoded proteins.

Given Data / Assumptions:

• Certain mitochondrial genomes reassign codons (e.g., UGA as tryptophan in human mitochondria).
• Start and stop assignments may differ.
• Question asks if organelle codes differ from prokaryotic standard.

Concept / Approach:Organelle translation systems evolved specialized tRNAs and factors, leading to codon reassignments. Hence, their codes differ from the canonical bacterial code, even though many codons are the same.

Step-by-Step Solution:

Verification / Alternative check:Translation tables (e.g., NCBI genetic codes) list multiple alternative codes for mitochondria and some nuclear lineages.

Why Other Options Are Wrong:

• Exactly the same: contradicted by known reassignments.
• Partially the same but identical: internally inconsistent.
• None: a clear, accurate statement exists.

Common Pitfalls:Assuming “universal” means no exceptions; in practice, exceptions are critical in sequence annotation.

Final Answer:It differs from that used in prokaryotes