4 Eukaryotes C - Molecular Biology Part IV: Eukaryotes...

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1 Molecular Biology Part IV: Eukaryotes Regulation, Hyperdrive, & the C-Value Paradox C. regulating gene expression through mRNA stability & structure
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2 mRNA general structure stability: roles of different parts of mRNA introduction to introns
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3 Ross 1989 Scientific American Unique to eukaryotes 5’ cap general mRNA structure -- eukaryotes poly-A tail added after transcription
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4 poly-A tail makes it easy to isolate eukaryotic mRNA on chromatography columns: beads with poly-T bind mRNA Reverse Transcriptase makes cDNA from mRNA; this can be cloned, amplified by PCR, etc. for study
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5 mRNA caps
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6 in contrast to prokaryotes, euk. mRNA varies greatly in stability hence part of gene expression, beyond transcription, results from mRNA stability mRNA half life: prokaryotes ~ a few minutes, eukaryotes ~ hours Hb mRNA translated ca. 17,000 times!
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7 Ross 1989 Scientific American mRNA turnover can be rapid in-situ probing of Drosophila blastula for abl mRNA black dots = radiolabeled probe same probe, 30 min later
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8 mRNA stability: tests especially studied in vitro , with cell-free systems stability can be affected by: cap (more later) 5’ leader coding region 3’ trailer poly-A tail (more later)
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9 Ross 1989 Scientific American differential stability of mRNA: B-globin vs. histone in-vitro assay: radiolabeled mRNA plus extract of lysed cells histone mRNA degraded faster than B-globin mRNA in cell-free assay
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10 stability: 5’ leader c- myc gene: a proto-oncogene encodes normal protein in normal cells if altered, or if too much made, cell becomes cancerous normal c- myc mRNA half-life = 10 min cancerous c- myc : mRNA half-life = 30-50 min mRNA the same except in 5’ leader– protein unchanged
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11 Ross 1989 Scientific American Stability: coding portion– altering length can affect stability Histone mRNA
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This note was uploaded on 12/24/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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4 Eukaryotes C - Molecular Biology Part IV: Eukaryotes...

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