Which of the following discoveries is most crucial to explaining why all organisms share the same genetic code? Vesicles containing the same organelles
Microspheres' similarities to modern meteorites
RNA's ability to self-catalyze
DNA's ability to absorb carbon molecules

RNA's ability to self-catalyze.

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I believe the answer is Intron IV, Introns are non-coding regions while exons are the coding regions. In most eukaryotic genes, coding regions (exons) are interrupted by non coding regions (introns). During transcription, the entire gene is copied into a pre-mRNA splicing, introns are removed and exons joined to form a contiguous coding sequence.