BIOL 2100 Chapter Notes - Chapter 18.3 + 18.5: X-Inactivation, Tumor Suppressor Gene, Small Interfering Rna
25 Nov 2016
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Document Summary
Genes for rna and trna only compose of a small portion of non-protein coding dna. About 75% of the genome is transcribed at any given point. Micrornas = can bind to complementary sequences in mrna molecules. Mirna allows the complex to bind to any mrna molecule with at least 7 to 8 nucleotides of the complementary sequence. The mirna-protein complex then either degrades the mrna or stops transcription. Expression of one-half of human genes is regulated by mirnas. Small interfering rnas (sirnas) = similar to mirnas in function, except that sirnas have a precursor of a double-stranded rna molecules. Rna interference (rnai) = blocking of gene expression by sirna. One possible source of the evolution of rnai is that it can stop viruses that have double- stranded rna. Sirnas can reform heterochromatin in some yeasts. Sirna system interacts with other noncoding rnas and chromatin modifying enzymes.
