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Eukaryotic organisms have essential differences in cell structure compared with prokaryotic ones. Eukaryotes have typical cell structure, mitosis and meiosis. That’s why their structure of gene and genome is different from prokaryotic genetic machinery.
There is great divergence of sequence between a given intron in different eukaryotic organisms. The exon sequences are much more conserved. This suggests that the actual sequence of the intron is not very important. If it were important, then any changes that occurred during evolution would be damaging, and the organisms with the changes would not be likely to survive.
RNA splicing is carried out by snRNPs which stands for small nuclear RNA containing ribonucleoprotein particles. The snRNPs contain both RNA and proteins. (Each snRNP contains a molecule of snRNA.) In this respect they are very similar to ribosomes, another RNP particle in the cell. In snRNPs, the RNA carries out enzymatic duties, and the proteins hold the snRNPs in the correct configuration to stabilize them.
There is an evolutionary benefit to having introns; otherwise, the energy cost to splice would not be compensated.
Sometimes splicing skips over an exon. For example say the pre-mRNA contains A-B-C-D exons. Splicing in some tissues might lead to an A-B-D mRNA (exon C is skipped). Or the splicing could produce an A-C-D mRNA (exon B is skipped). These mRNAs would have the same end exons but different middles. They will code for different proteins. This alternative splicing uses genetic expression to facilitate the synthesis of a greater variety of proteins.
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