MBB 222 Lecture Notes - Lecture 30: Phillip Allen Sharp, Nucleotidyltransferase, Ribonuclease P
20 Dec 2018
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Not just mrna that get spliced, eg trna maturation: rnase p is a ribozyme, trna nucleotidyltransferase adds cca to 3" end with no template, splicing in this case takes place outside the nucleus. Splicing was first detected by r-looping . ssdna was hybridized to its corresponding mrna and imaged by electron microscopy. Large loops of dna were observed that did not anneal. These loops encode introns that are excised out of the pre-mrna to make the mrna molecule. The presence of introns can also be demonstrated by comparing the sequence of a gene to that of its corresponding complementary dna (cdna), which is synthesized from the mrna. The discovery of introns led to the nobel prize in physiology or medicine in 1993 for phillip allen. Exons are less than 1000 nucleotides (nt), and typically 100-200 nt long, in eukaryotes. Typically much more dna is devoted to introns than exons.
