Chapter 15 Gene Regulation 2 Outline Prokaryotic Regulation
- Slides: 35
Chapter 15 Gene Regulation
2 Outline Prokaryotic Regulation trp Operon lac Operon Eukaryotic Regulation Transcriptional Control Posttranscriptional Control Translational Control Posttranslational Control Genetic Mutations Cancer
Prokaryotic Regulation: The Operon Model Operon consist of three components Promoter DNA sequence where RNA polymerase first attaches Short segment of DNA Operator DNA sequence where active repressor binds Short segment of DNA Structural Genes One to several genes coding for enzymes of a metabolic pathway Translated simultaneously as a block Long segment of DNA 3
Repressible Operons: The trp Operon The regulator codes for a repressor If tryptophan (an amino acid) is absent: Repressor is unable to attach to the operator (expression is normally “on”) RNA polymerase binds to the promoter Enzymes for synthesis of tryptophan are produced If tryptophan is present: Combines with repressor as corepressor Repressor becomes functional Blocks synthesis of enzymes and tryptophan 4
The trp Operon 5
Inducible Operons: The lac Operon 6 The regulator codes for a repressor If lactose (a sugar that can be used for food) is absent: Repressor attaches to the operator Expression is normally “off” If lactose is present: It combines with repressor and renders it unable to bind to operator RNA polymerase binds to the promoter The three enzymes necessary for lactose catabolism are produced
The lac Operon 7
Action of CAP 8
9 Eukaryotic Regulation A variety of mechanisms Five primary levels of control: Nuclear levels Chromatin Packing Transcriptional Control Posttranscriptional Control Cytoplasmic levels Translational Control Posttranslational Control
Regulation of Gene Expression: Levels of Control in Eukaryotes 10
11 Chromatin Structure Eukaryotic DNA associated with histone proteins Together make up chromatin As seen in the interphase nucleus Nucleosomes: DNA wound around balls of eight molecules of histone proteins Looks like beads on a string Each bead a nucleosome The levels of chromatin packing determined by degree of nucleosome coiling
Levels of Chromatin Structure 12
13 Chromatin Packing Euchromatin Loosely coiled DNA Transcriptionally active Heterochromatin Tightly packed DNA Transcriptionally inactive Barr Bodies Females have two X chromosomes, but only one is active Other is tightly packed along its entire length Inactive X chromosome is Barr body
X-Inactivation in Mammalian Females 14
15 Transcriptional Control Transcription controlled by proteins called transcription factors Bind to enhancer DNA Regions of DNA where factors that regulate transcription can also bind Always present in cell, but most likely have to be activated before they will bind to DNA
Lampbrush Chromosomes 16
Initiation of Transcription 17
18 Posttranscriptional Control Posttranscriptional control operates on primary m. RNA transcript Given a specific primary transcript: Excision of introns can vary Splicing of exons can vary Determines the type of mature transcript that leaves the nucleus May also control speed of m. RNA transport from nucleus to cytoplasm Will affect the number of transcripts arriving at rough ER And therefore the amount of gene product realized per unit time
Processing of m. RNA Transcripts 19
20 Translational Control - Determines degree to which m. RNA is translated into a protein product Presence of 5′ cap Length of poly-A tail on 3′ end Posttranslational Control - Affects the activity of a protein product Activation Degradation rate
Effect of Mutations on Protein Activity 21 Point Mutations Involve change in a single DNA nucleotide Changes one codon to a different codon Affects on protein vary: Nonfunctional Reduced functionality Unaffected Frameshift Mutations One or two nucleotides are either inserted or deleted from DNA Protein always rendered nonfunctional Normal : After deletion: After insertion: THE CAT ATE THE RAT THE ATA TET HER AT THE CCA TAT ETH ERA T
Point Mutation 22
23 Faulty Proteins = Genetic Disorders Examples: Sickle cell anemia Hemophilia PKU Albinism Huntington’s Disease Androgen insensitivity
Androgen Insensitivity 24
25 A (phe) Ea B (tyr) Eb C (Melanin)
Error in Enzyme a 26
27 The gene that produces this enzyme is on chromosome 9
28 The blood in the retina and iris reflects red light, resulting in pink
29 We will revisit this section after Mendelian Genetics! TEST ON WED! Ch 14 and Ch 15
30 Carcinogenesis Development of cancer involves a series of mutations Proto-oncogenes – Stimulate cell cycle Tumor suppressor genes – inhibit cell cycle Mutation in oncogene and tumor suppressor gene: Stimulates cell cycle uncontrollably Leads to tumor formation
Carcinogenesis 31
Achondroplasia and Xeroderma Pigmentosum 32
33 Causes of Mutations Replication Errors 1 in 1, 000, 000 replications DNA polymerase Proofreads new strands Generally corrects errors Environmental Mutagens Carcinogens - Mutagens that increase the chances of cancer Ultraviolet Radiation Tobacco Smoke
34 Review Prokaryotic Regulation trp Operon lac Operon Eukaryotic Regulation Transcriptional Control Posttranscriptional Control Translational Control Posttranslational Control Genetic Mutations Cancer
Ending Slide Chapter 15 Gene Regulation
- Chapter 17 gene expression from gene to protein
- Chapter 18 regulation of gene expression
- Chapter 18 regulation of gene expression
- Chapter 12 section 4 gene regulation and mutations
- Chapter 18 regulation of gene expression
- Chapter 18
- Operon lac
- Gene finding
- Gene by gene test results
- Section 4 gene regulation and mutation
- Gene regulation
- Section 12-5 gene regulation
- Regulation of gene expression in bacteria
- Prokaryotes vs eukaryotes gene regulation
- "manuales delorenzo"
- Section 12-5 gene regulation answer key
- What is gene regulation
- Gene regulation
- Differential gene regulation
- Positive control vs negative control gene expression
- Sentence outline
- Molecular biology of the gene chapter 10
- Mendel and the gene idea chapter 14
- Chapter 14 mendel and the gene idea
- Chapter 10 section 3 gene linkage and polyploidy
- Chapter 10: molecular biology of the gene
- Chapter 13 lesson 1 identifying the substance of the gene
- Chapter 17 from gene to protein
- Molecular biology of the gene chapter 10
- Chapter 17 from gene to protein
- Molecular biology of the gene chapter 10
- Chapter 14 mendel and the gene idea
- Chapter 14 mendel and the gene idea
- Chapter 14 mendel and the gene idea
- Chapter 14 mendel and the gene idea
- Is a venus fly trap prokaryotic or eukaryotic