GCD 3022 1st Edition Lecture 24Outline of Last Lecture I. Overview of Epigeneticsa. Epigeneticsb. Epigenetic inheritance c. Epigenetic regulationII. Cis and trans epigenetic changesa. Cis epigenetic changesb. Trans epigenetic changesIII. Epigenetics and developmenta. Process of developmentb. Epigenetic regulationIV. Genomic imprintinga. Igf2 gene and methylationb. CTC-binding factorV. Development of specific cell typesa. Embryonic developmentb. Polycomb group (PcG)c. Inhibition of transcriptionVI. Regulation of RNA processingThese 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.a. Alternative splicingb. Alpha-tropomyosinc. Splicing factorsVII. mRNA stabilitya. regulation of stabilityb. factors that affect stabilityi. length of polyA tailii. destabilizing elementsc. RNA interferencei. miRNAii. double stranded RNAs Outline of Current LectureI. RNA interferencea. Definitionb. ProcessII. Genetic Imprintinga. Igf2 geneb. ICR mutationIII. mRNA degradationa. mRNA half-lifeb. advantages and disadvantages of short half-lifec. advantages and disadvantages of long half-lifeIV. Alternative splicinga. Exampleb. ExplanationCurrent LectureI. RNA interferencea. Definition: also known as RNAi, this mechanism of RNA modification involves a double stranded RNA known as micro-RNA (or miRNA). This type of RNA does not code for proteins but instead hybridizes with mRNA, which has a direct effectgene expression.b. Process: RNAi leads to silencing of gene expression by using the double stranded miRNAs to pair with mRNA, which prevents the gene from being expressed. II. Genetic Imprinting: method of epigenetic inheritance in which one parental allele is inactivated during gametogenesis (formation of egg or sperm).a. Igf2 gene: common example of genetic imprinting in which the male’s sperm is methylated during spermatogenesis and the female’s eggs are not methylated. This results in the male’s Igf2 gene being active and the female’s inactive.b. ICR mutation: a mutation to the imprinting control region in the female’s DNA will probably not change whether the Igf2 gene is expressed or not. Since the female’s DNA is not methylated, CTC factors bind to the ICR and DMR and these factors cause the formation of a loop in the DNA which renders it inactive. With the removal of the ICR, only one CTC could bind to the DMR but this may still be enough to inactivate the gene. III. mRNA degradation: occurs as the mRNA ages and the polyA tail shortens.a. mRNA half-life: the unit of time that determines how long an mRNA will last. Thiscould be hours, days, or even months depending on the mRNA molecule.b. Advantages and disadvantages of short half-life: an advantage of a short half-life are that it allows more adaptability in regulation of protein production and a disadvantage is that it is inefficient at making mRNA consistently.c. Advantages and disadvantages of long half-life: an advantage of a long half-life might is that they don’t have to remake mRNA constantly and a disadvantage is that it might end up expressing a protein that is not necessary for the cell. IV. Alternative splicing: splicing of pre-mRNA may produce different codons depending on how it is spliced and which splicing factors act on it. a. Example: a gene has four exons, and some cell types of the mature mRNA contain all four exons while others are missing exon 3. It is suspected that the cells that lack exon 3 express a splicing repressor. Determine which splice site thisrepressor acts on. b. Explanation: the repressor acts on the 3’ splice site of the third intron. The spliceosome can then assemble normally at the 5’ splice site of intron 3, but doesnot recognize the 3’ site so it splices both the intron and the exon, removing exon3 from the molecule. The spliceosome then continues splicing the rest of the molecule leaving exons 1,2, and
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