Biology Seventh Edition Solomon Berg Martin Chapter 13

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Gene regulation in bacteria and eukaryotes • Bacterial cells – Grow rapidly and have short life span – Transcriptional-level control best • Eukaryote cells – Long life span – Gene regulation complex – Transcriptional-level control dominates, but other levels important, also Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Gene regulation in bacteria • Most organized into operons – Gene complex plus linked DNA – Each has single promoter region upstream • Operator regulates transcriptional-level control of operon – When repressor protein binds to operator, it prevents transcription – Binds specifically to the lac operator sequence Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation The lac operon Copyright © 2005 Brooks/Cole

Biology, Seventh Edition CHAPTER 13 Gene Regulation Genetic and biochemical characterization of the lac

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Inducible, repressible, and constitutive genes • Inducible operon, such as lac operon, normally turned off • Repressible operon, such as the trp operon, normally turned on • Constitutive genes – Neither inducible nor repressible – Active at all times Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation The trp operon Copyright © 2005 Brooks/Cole

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Negative regulators inhibit transcription • Repressible and inducible operons • When repressor protein binds to the operator, transcription is turned off • Positive regulators stimulate transcription • Some inducible operons • Regulated by activator proteins Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation Positive control of the lac operon Copyright

Biology, Seventh Edition CHAPTER 13 Gene Regulation Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation A regulon Copyright © 2005 Brooks/Cole —

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Gene regulation in eukaryotic cells • Not organized into operons • Gene regulation occurs at the levels of – Transcription – m. RNA processing – Translation – The protein product Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Eukaryotic promoters vary in efficiency, depending on UPEs • Promoter consists of –RNA polymerase-binding site –Upstream promoter elements (UPEs) • Number and types of UPEs determine efficiency • Inducible eukaryotic genes controlled by enhancers Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation of transcription in eukaryotes Copyright © 2005

Biology, Seventh Edition CHAPTER 13 Gene Regulation Regulatory proteins Copyright © 2005 Brooks/Cole —

Biology, Seventh Edition CHAPTER 13 Gene Regulation Stimulation of transcription by an enhancer Copyright

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Chromosome organization may affect gene expression • Genes are inactivated by changes in chromosome structure • DNA methylation is mechanism that perpetuates gene inactivation • Multiple copies of some genes present in one chromosome • Gene amplification Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 13 Gene Regulation • Differential m. RNA processing • Cells in each tissue produce own version of m. RNA • For example, different forms of troponin, a protein that regulates muscle contraction, produced in different muscle tissue Copyright © 2005 Brooks/Cole — Thomson Learning