Chapter 14 Regulation of Genome Activity 1. Transient Changes in Genome Activity 2. Permanent and semipermanent changes in Genome Activity 3. Regulation of Genome Activity During Development
Chapter 14 Regulation of Genome Activity 1. Transient Changes in Genome Activity 2. Permanent and Semipermanent Changes in Genome Activity 3. Regulation of Genome Activity During Development
Table 14.1 Examples of steps in the genome expression pathway at which regulation can be exerted Example of regulation Transcription Gene accessibility Locus control regions determine chromatin structure in areas that contain genes (Section 10.1.2) Histone modifications influence chromatin structure and determine which genes are accessible(Section 10.2.1) Nucleosome positioning controls access of RNA polymerase and transcription factors to the promoter region (Section 10. 2.2 DNA methylation silences regions of the genome( Section 10.3.1) Initiation of transcription Productive initiation is influenced by activators, repressors, and other control systems (Section 11.3) Synthesis of RNA Prokaryotes use antitermination and attenuation to control the amount and nature of individual transcripts(Section 12. 1. 2)
Table 14.1 Examples of steps in the genome expression pathway at which regulation can be exerted Step Example of regulation Eukaryotic mRNA Processing Capping Some animals use capping as a means of regulating protein synthesis during egg maturation adenylation Alternative polyadenylation sites control flowering in Arabidopsis Translation of bicoid mRNA in Drosophila eggs is activated after fertilization by extension of the poly (A)tail(Section 14.3.4) Alternative splice site selection controls sex determination in Drosophila(Section 12.2. 2) Chemical modification RNA editing of apolipoprotein-B mRNA results in liver-and intestine-specific versions of this protein(Section 12.2.5) mRNA degradation MicroRNAs control cell death, specification of neuron cell types, and control of fat storage in Caenorhabditis elegans, as well as many diverse processes in other eukaryotes (Section 12.2.6) Iron controls degradation of transferrin receptor mRNA(Section 13. 2.2)
Table 14. 1 Examples of steps in the genome expression pathway at which regulation can be exerted Step Example of regulation Protein synthesis and processing Initiation of translation Phosphorylation of elF-2 results in a general reduction in translation initiation in eukaryotes (seon1322) Ribosomal proteins in bacteria control their own synthesis by modulating ribosome attachment to their mRNAs(Section 13. 2.2) In some eukaryotes, iron controls ribosome scanning on ferritin mRNAs(Section 13. 2.2) Small RNAs in bacteria regulate the response to oxidative stress by modulating initiation of translation of various mRNAs(Section 13. 2.2) Protein synthesis Frameshifting enables two DNA polymerase lll subunits to be translated from the Escherichia coli dnax gene(Section 13.2.3 Cutting events Alternative cleavage pathways for polyproteins result in tissue-specific protein products (Section 13.3.2) Chemical modification Many proteins involved in signal transduction are activated by phosphorylation (Section 14. 1.2)
How the activity of the genome as a whole is requlated Differentiation not only in multicellular organisms Human has over 250 types of specialized cells
How the activity of the genome as a whole is regulated. • Differentiation not only in multicellular organisms. • Human has over 250 types of specialized cells