BBMB 405 1st Edition Lecture 38Outline of Last Lecture XVII. Chapter 32: The control of gene expression in eukaryotesC. The control of gene expression can require chromatin remodelingD. Transcription factors bind DNA and regulate transcription initiationOutline of Current Lecture XVII. Chapter 32: The control of gene expression in eukaryotesE. Eukaryotic Gene Expression can be controlled at posttranscriptional levelsXVIII. Chapter 33: Sensory SystemsA. A wide variety of organic compounds are detected by olfactionCurrent LectureXVII. Chapter 32: The control of gene expression in eukaryotesE. Eukaryotic Gene Expression can be controlled at posttranscriptional levels1. Biogenesis of miRNAs and formation of RISCa. microRNA needs to be cleaved, cleavage along dsRNAb. Create 21 to 25 nucleotidesc. In duplex, contains 3’ end overhandsd. Duplex unwound and one strand is chosen as a guide to form silencing complexe.2. Dicer and Argonaute (Ago) recognize RNA endsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3. Posttranscriptional silencing by RISCa. RISC binds to sequences in 3’-UTR of mRNAs that match miRNAb. Complementarity is required only in seed or positions 2 to 8 miRNA sequencec. Some mRNAs have more than one miRNA target sequencesd.e. Complete complementarity between guide RNA and mRNA leads to endonucleolytic cleavage, most common in siRNA pathwayf. Mismatches between guide RNA and mRNA will lead to translational repression or destabilization of mRNA, most common in miRNA pathway4. miR-206 represses estrogen receptora. Estrogen receptor (ER) mRNA is susceptible to post-transcriptional regulation by miRNA-206b. Breast cancers have low levels of miR-206; miR-206 levels are inversely relatedto levels of ER mRNAc. Introduction of miR-206 into breast cancer cells inhibits cell growth in a dose- and time-dependent manner; it is a potential therapeutic but RNA is difficult to deliverXVIII. Chapter 33: Sensory SystemsA. A wide variety of organic compounds are detected by olfaction1. How do we perceive the physical world?a. Stimuli leads to detection of physical eventb. Signals are sent through receptors expressed in sensory neurons; specific receptors have specific signalsc. Signals are transmitted to central nervous system by specific neurons2. Smell: Detection of organic compounds by olfactiona. Odorants stimulate smellb. Properties of odorants: volatility (easier transport to olfactory system); small organic compounds (generally smaller than 300 Da); shape of molecule determines interactions with receptor3. Stereoisomers can have significantly different olfactory propertiesa. Chemically indistinct except for shape: example R-carvone smells like spearmint and S-carvone smells like carawayb.c. Likely interact differently with protein receptor, suggesting that protein receptors recognize odorant shape4. Olfaction is mediated by receptors in nasal epitheliuma. Transmembrane receptors are found in cilia and synapses of sensory neurons; G protein-coupled receptors (GPCRs)b.5. Olfactory receptors (OR)a. Rats contain more than 1000 genes expressing olfactory receptors; humans have about 350 but about 500 pseudogenes or nonfunctional versionsb. Each OR can recognize several different odorants to different degreesc. Only one type expressed per olfactory neuron; combinatorial activation enables differentiation between odors6. Genetic variations in OR genes may cause change taste perceptiona. SNP identified in cilantro haters is located near cluster of olfactory receptorsb. One of nearby genes (OR6A2) detects aldehydes that make cilantro smell
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