MCDB 1A Chapter Notes - Chapter 16: Proteasome, Guanosine Triphosphate, Lysine
10 Oct 2016
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Eukaryotic gene expression can be regulated both in the nucleus prior to mrna export and after mrna leaves the nucleus. Different mrnas can be made from the same gene by altering splicing. Before rna exports nucleus, splicing mechanism recognizes exons and introns. -> convert pre-mrna, which has introns, into mature mrna which does not. Pre-mrna (introns + all exons) --splicing--> mrna (exons only) For some genes, alternative splicing can occur, where some exons are spliced out along with the introns. Controlled by regulatory elements in rna sequence that bind specific proteins and by secondary rna structures that form by hybridization between nucleotides in single-stranded rna molecule. Small rnas are important regulators of gene expression. Microrna (mirna) = tiny molecules that are noncoding regions but transcribed as longer precursors that fold into double-stranded rna molecules and are then processed into single stranded mirnas. Mirnas synthesized from dna sequences separate from their targets whereas sirna are targeted to their sequence of origin.
