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Biology LibreTexts

12.S: Regulation of Gene Expression (Summary)

  • Regulation of gene expression is essential to the normal development and efficient functioning of cells
  • Gene expression may be regulated by many mechanisms, including those affecting transcript abundance, protein abundance, and post-translational  modifications
  • Regulation of transcript abundance may involve controlling the rate of initiation and elongation of transcription, as well as transcript splicing, stability, and turnover
  • The rate of initiation of transcription is related to the presence of RNA polymerase and associated proteins at the promoter. 
  • RNApol may be blocked from the promoter by repressors, or may be recruited or stabilized at the promoter by other proteins including transcription factors
  • The lac operon is a classic, fundamental paradigm demonstrating both positive and negative regulation through allosteric effects on trans-factors.
  • In eukaryotes, cis-elements that are usually called enhancers bind to specific trans-factors to regulate transcriptional initiation. 
  • Enhancers may be modular, with each enhancer and its transcription factor regulating a distinct component of a gene’s expression pattern, as in the yellow gene.
  • Sticklebacks provide examples of recent evolutionary events in which mutation of an enhancer produced a change in morphology and a selective advantage.
  • Chromatin structure, including reversible modifications such as acetylation of histones, and methylation DNA CpG sites also regulates the initiation of transcription.
  • Chromatin modifications or DNA methylation of some genes are heritable over many mitotic, and sometimes even meiotic divisions.
  • Heritable changes in phenotype that do not result from a change in DNA sequence are called epigenetic.  Many epigenetic phenomena involve regulation of gene expression by chromatin modification and/or DNA methylation.

Key Terms:

gene expression

transcriptional regulation

operon

lactose

glucose

lac operon

lacZ

lacY

lacA

galactosidase

permease

trans-acetylase

P  /  promoter

O  /  operator

CBS

CAP-binding site

cis-elements

trans-regulators

lacI

homotetramer

repressor

allosteric

cAMP binding protein

CAP

CAP binding sequence

CBS

adenylate cyclase

constitutive

Oc  /  I-   /   Is

F-factor / episome

GC boxes

CAAT boxes

TATA boxes

GAL4-UAS

Driver/responder

transcription start site

enhancers/silencers

transcription factors

hemoglobin/heme/globin

pseudogene

gene families

stickleback

primordium

chromatin remodeling

acetylation/deacetylation

methylation/demethylation

CpG sites

epigenetics

winter annual

vernalization

FLC

 

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