BIOL 1107 1nd Edition Lecture 23Outline of Current Lecture I. Mis-sense mutationII. Non-senseIII. SilentIV. FrameshifV. DeletionOutline of Current Lecture I. Gene Expression (Prokaryotic)II. Gene RegulationIII. TerminologyIV. Gene Expression (Eukaryotic)Current LectureI. Gene Expression - National Human Genome Research Instituteo How many genes in the human body? 24,000 geneso Every single cell has these genes- Gene Expression (two classes of genes)o Housekeeping- always expressed, cellular respiration, actin/microtubules for shapeo Regulated genes- melanin, digestive enzymesII. Gene Regulation - How do we regulate genes? DNA binding proteins (TATA binding proteins)- Turning a gene on (positive regulation)- Turning a gene off (negative regulation)These 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.- Tryptophan- essential amino acid; get it from foodo E-coli can make their own tryptophan- How do cells control multiple genes at the same time?o Prokaryotes- operons- Trp operon- Why would the cell want to stop tryptophan synthesis? Too much tryptophan activates repressor, which stop RNA synthesis- How is this operon regulated?- Lac operon- Lactose utilization- Lac operon -> negative and positive regulation- Sensing glucose levels- presence of glucose (turns lac operon off), no presence of glucose (turns lac operon on)- When glucose is low:- When glucose is high: - Under what conditions will bacteria strongly express lac operon? In the presence of lactose but not glucoseIII. Terminology- Negative regulation: repressor protein stopping/blocking transcription- Repressor: binds to the operator and blocks attachment of RNA polymerase to the promoter, preventing transcription of the genes- Co-repressor: a small molecule that cooperates with a repressor protein to switch an operon off- Positive regulation: turning on of the structural gene expression by the active repressor protein - Activator: a protein that binds to DNA and stimulates transcription of a gene- Co-activator: a protein that increases gene expression by binding to an activator (or transcription factor) which contains a DNA binding domain. The co-activator is unable to bind DNA by itself.- Inducer: inactivates the repressorIV. Eukaryotic Gene Expression- Regulation occurs at many levels- DNA packaging o Histones, nucleosomes, protein scaffold - DNA + protein scaffold = chromatino Heterochromatin- very tightly packedo Euchromatin- loosely packed (has more gene expression. Why? Easier to get to)- Transcriptional control- Post transcriptional controlo Protein processing, protein
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