Organelles? that'd be my geuss
The correct answer is: introns
Processing of mRNA is process that occurs only in eukaryotic cells. After the transcription, newly formed mRNA molecule is called and it must be processed into a messenger RNA (mRNA). Processing includes:
• Addition of a 5' cap to the beginning of the RNA
• Polyadenilation- addition of a poly-A tail (tail of A nucleotides) to the end of the RNA
• Splicing- removal of introns and linking the exons
After these steps mRNA is mature and used for the further steps (e.g. translation).
Sometimes some genes are alternatively spliced.
Different enzymes have specific active sites which can only catalyze one <span>substrate. Enzyme-substrate complexes are produced only when the substrate fits into the active site :)</span>