consider the following…
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Consider the following…. Do all of the cells in your body carry out the same processes? Do all of the cells in your body make the same proteins? Do all of the cells in your body contain the same genes? What is the connection between genes and protein production? - PowerPoint PPT PresentationTRANSCRIPT
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Consider the following…
• Do all of the cells in your body carry out the same processes?
• Do all of the cells in your body make the same proteins?
• Do all of the cells in your body contain the same genes?
• What is the connection between genes and protein production?
• How is it possible for different types of cells to exist in your body?
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Gene Expression & The Lac Operon
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Other Kinds of Operons
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Cell Differentiation•Differentiation is when cells become specialized in structure and function•It results from selective gene expression, the turning on and off of specific genes.
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Turning Eukaryotic Genes On & Off
•Eukaryotic RNA polymerase needs assistant transcription factor proteins•Activator proteins bind to enhancers (not adjacent to the gene)•DNA bends & interacts with other transcription factors, facilitating correct RNA polymerase attachment
Gene Switches
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DNA Packing Helps Regulate Eukaryotic Gene Expression•A single chromosome contains app. 4cm of DNA•Coiling and folding enables all this DNA to fit in the nucleus•This packing prevents gene expression by blocking transcription proteincontact with DNA•Some regions of interphase chromosomes (chromatin) are highly packed like mitotic chromosomes •The genes in these packed regions are generally not expressed
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X chromosome Inactivation• Female mammals
inherit 2 X chromosomes, but do not make twice as much X-coded proteins
• One X in each somatic cell condenses into a compacted, inactive Barr body.
• The same X is not turned off in every cell
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X Inactivation & Cat Fur - Tortoiseshell
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X Inactivation & Cat Fur - Calico
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Alternative RNA Splicing• More than one type of polypeptide can result from a
single gene• Different exons are spliced together as a result of
alternative splicing
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Homeotic Genes• Master control genes that
regulate the genes that actually control the anatomy of body parts
• Discovered by studying bizarre fruit fly mutations
• Mutation in a single gene led to legs growing out of head in place of antennae
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Epigenetics
• Heritable traits that do not involve changes in the underlying DNA sequence (“in addition to changes to the genetic sequence”)
• Used to describe any aspect other than DNA sequence that influences the development of an organism.
• Involves chemical modifications that “mark” certain genes with a distinct signature; “biological punctuation”
ex) Doctors v. Doctor’s
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The Agouti Mice
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When Epigentics Meets Pediatrics
• What is meant by the terms “epigenetics” and the “epigenome”?
• Identify chemical groups known to modify genes and influence gene expression.
• What is meant by the phrase “epigenetic signatures”?
• How are epigenetic effects different from genetic effects?
• What contributes to our epigenetic make-up or profile?
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DNA Microarray (“DNA chip” /”Gene Chip”)
• Isolate mRNA transcribed from genes in selected cell
• Mixed with reverse transcriptase to form cDNA (complementary) fragments with fluorescent nucleotides
• Add cDNA to fixed DNA fragments in microarray tray
• cDNA binds to complementary bases producing a detectable glow
• Non-binding DNA rinsed away
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