* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download gene regulation
Genomic imprinting wikipedia , lookup
Long non-coding RNA wikipedia , lookup
Genome evolution wikipedia , lookup
Cancer epigenetics wikipedia , lookup
Epitranscriptome wikipedia , lookup
Gene expression programming wikipedia , lookup
Gene therapy wikipedia , lookup
X-inactivation wikipedia , lookup
Oncogenomics wikipedia , lookup
Minimal genome wikipedia , lookup
Genetic engineering wikipedia , lookup
Epigenetics in stem-cell differentiation wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Point mutation wikipedia , lookup
Gene expression profiling wikipedia , lookup
Genome (book) wikipedia , lookup
History of genetic engineering wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Microevolution wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Mir-92 microRNA precursor family wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Designer baby wikipedia , lookup
Primary transcript wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Chapter 11 The Control of Gene Expression PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings To Clone or Not to Clone? • A clone is an individual created by asexual reproduction and thus is genetically identical to a single parent – Cloning an animal using a transplanted nucleus shows that an adult somatic cell contains a complete genome • Cloning has potential benefits but evokes many concerns – Does not increase genetic diversity – May produce less healthy animals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings GENE REGULATION 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes • Gene regulation is the "turning on" and "turning off" of genes – Helps organisms respond to environmental changes • Gene expression is the process by which information flows from genes to protein • Early understanding of gene control came from studies of the bacterium Escherichia coli Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings GENE REGULATION • An operon is a cluster of genes with related functions, along with two control sequences – Promoter: A sequence of genes where the RNA polymerase attaches and initiates transcription – Operator: A sequence of genes between the operon and the promoter that acts as a switch for the binding of RNA polymerase • A repressor binds to the operator, stopping transcription • A regulatory gene, located outside the operon, codes for the repressor Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings GENE REGULATION • The lac operon contains the genes that code for the enzymes that metabolize lactose – Repressor is active when alone and inactive when bound to lactose • The trp operon allows bacteria to stop making tryptophan when it is already present – Repressor is inactive alone; must bind to the amino acid tryptophan to be active Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-1b OPERON Regulatory gene Promoter Operator Lactose-utilization genes DNA mRNA Protein RNA polymerase cannot attach to promoter Active repressor Operon turned off (lactose absent) DNA RNA polymerase bound to promoter mRNA Protein Lactose Inactive repressor Operon turned on (lactose inactivates repressor) Enzymes for lactose utilization LE 11-1c Promoter Operator Genes DNA Active repressor Active repressor Tryptophan Inactive repressor Inactive repressor Lactose lac operon trp operon GENE REGULATION 11.2 Differentiation yields a variety of cell types, each expressing a different combination of genes • Gene regulation is much more complex in eukaryotes than in prokaryotes – In multicellular eukaryotes, cells become specialized as a zygote develops into a mature organism – The particular genes that are active in each type of cell are the source of its particular function Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-2 Muscle cell Pancreas cells Blood cells GENE REGULATION 11.3 Differentiated cells may retain all of their genetic potential • Though differentiated cells express only a small percentage of their genes, they retain a complete set of genes – Allows for propagation of crop plants – In animal cells can lead to regeneration Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-3 Root of carrot plant Single cell Root cells cultured in nutrient medium Cell division in culture Plantlet Adult plant GENE REGULATION 11.4 DNA packing in eukaryotic chromosomes helps regulate gene expression • DNA can fit into a chromosome because of packing – DNA winds around clusters of histone proteins, forming a string of bead-like nucleosomes – The beaded fiber coils, supercoils, and further folds into chromosomes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-4 DNA double helix (2-nm diameter) Histones “Beads on a string” Linker Nucleosome (10-nm diameter) Tight helical fiber (30-nm diameter) Supercoil (300-nm diameter) 700 nm Metaphase chromosome DNA Splicing 11.7 Eukaryotic RNA may be spliced in more than one way • After transcription, splicing removes noncoding introns • Alternative splicing may generate two or more types of mRNA from the same transcript Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-7 Exons DNA RNA transcript RNA splicing mRNA or DNA Regulation 11.8 Translation and later stages of gene expression are also subject to regulation • After eukaryotic mRNA is processed and transported to the cytoplasm, there are additional opportunities for regulation – Breakdown of mRNA – Initiation of translation – Protein activation – Protein breakdown Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Regulation 11.9 Review: Multiple mechanisms regulate gene expression in eukaryotes • Cellular differentiation results from selective turning on or off of genes at multiple control points – In nucleus • DNA unpacking and other changes • Transcription • Addition of cap and tail • Splicing Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings DNA REGULATION – In cytoplasm • Breakdown of mRNA • Translation • Cleavage/modification/activation • Breakdown of protein • Each differentiated cell still retains its full genetic potential Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ANIMAL CLONING 11.10 Nuclear transplantation can be used to clone animals • Nuclear transplantation – Nucleus of a somatic cell is transplanted into a surrogate egg stripped of nucleus – Cell divides to the blastocyst stage • Reproductive cloning – Blastocycst is implanted into uterus – Live animal is born Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Therapeutic cloning – Embryonic stem cells are harvested from blastocyst – These cells give rise to all the specialized cells of the body Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-10 Donor cell Nucleus from donor cell Implant blastocyst in surrogate mother Remove nucleus Add somatic cell from adult donor from egg cell Clone of donor is born (reproductive cloning) Grow in culture to produce an early embryo (blastocyst) Remove embryonic stem cells from blastocyst and grow in culture Induce stem cells to form specialized cells (therapeutic cloning) CONNECTION 11.11 Reproductive cloning has valuable applications, but human reproductive cloning raises ethical issues • Reproductive cloning of nonhuman mammals is useful in research, agriculture, and medicine • There are many obstacles, both practical and ethical, to human cloning – Research continues in the absence of consensus Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings THE GENETIC CONTROL OF EMBRYONIC DEVELOPMENT 11.13 Cascades of gene expression and cell-tocell signaling direct the development of an animal • Studies of mutant fruit flies led to early understanding of gene expression and embryonic development • Before fertilization, communication between the egg and adjacent cells determines body polarity • A cascade of gene expression controls development of an animal from a fertilized egg • Master control homeotic genes regulate batteries of genes that shape anatomical parts Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-13a Eye Antenna Leg Head of a normal fruit fly Head of a developmental mutant Transduction 11.14 Signal transduction pathways convert messages received at the cell surface to responses within the cell • Signal transduction pathway – Signaling cell secretes signal molecules – Signal molecules bind to receptors on target cell's plasma membrane – Cascade of events leads to the activation of a specific transcription factor Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transduction – Transcription factor triggers transcription of a specific gene – Translation of the mRNA produces a protein Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings THE GENETIC BASIS OF CANCER 11.16 Cancer results from mutations in genes that control cell division • An oncogene can cause cancer when present in a single copy in a cell • A cell can acquire an oncogene from – A virus – A mutation in a proto-oncogene, a normal gene with the potential to become an oncogene Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings THE GENETIC BASIS OF CANCER • Tumor-suppressor genes – Normally code for proteins that inhibit cell division – When inactivated by mutation, can lead to uncontrolled cell division and tumors Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 11-16b Tumor-suppressor gene Mutated tumor-suppressor gene Normal growthinhibiting protein Defective, nonfunctioning protein Cell division under control Cell division not under control