BIO230H1 Lecture Notes - Lecture 6: Chromatin, Aconitase, Dicer
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BIO230H1 Full Course Notes
Verified Note
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Document Summary
Some mrnas are incompletely processed or damaged in the cytosol. Need to prevent production of aberrant protein which can be toxic to cells. Recall trnas match animo acids to codons (3 nucleotides) in the mrna: genetic code. Eukaryotes mrna quality control in the cytosol translation initiation machinery recognizes 5"cap and poly-a tail. Exon junction complex (ejc) also stimulates translation ensuring proper slicing. Nonsense-mediated mrna decay: prominent mrna surveillance system, surveys for nonsense stop codons in the wrong place that is an indicator of improper splicing, normal splicing: ribosome binds to mrna as it emerges from nuclear pore. No ejc bound when ribosome reaches stop codon. mrna released to cytosol: abnormal splicing: ribosomes binds to mrna as it emerges from the nuclear pore. Stop codon is premature and ejcs remain on mrna when ribosome reaches stop. mrna degraded, mediated by. Cells can degrade aberrant mrna and allow functional protein to accumulate. Also have quality control for incomplete or broken mrnas.
