Gene Expression

Gene Expression

1. Regulatory gene

   • these genes are expressed continuously and at a low rate, they also create the repressor
   • differential gene expression
     • the expression of different genes by cells with the same genome
   • mutation in regulatory gene
     • a mutation may lead to the increased production of a certain gene, which can lead to cancer

2. Operons

   • lactose operon
     • can be switched off by the lac repressor, which is active by itself
     • inducer
       • a small molecule that inactivates the repressor
   • inductible operon
     • an operon whose synthesis is induced by a chemical signal
   • operator
     • an "on-off switch" that controls a cluster of functionally related genes, it controls the access of RNA polymerase to the genes
   • the operator, the promoter, and the genes they control make up an operon

3. Types of cells

   • Prokaryotic
     • a single-celled organism that has a nucleus but no organelles
   • Eukaryotic
     • cells found in multicellular organisms that have a nucleus and organelles

4. Molecules,Enzymes, and Proteins

   • repressor
     • binds to the operator and blocks attachment of RNA ploymerase to the promoter, preventing the transcription of genes
   • promoter
     • a site where RNA polymerase binds to DNA and begins transcription
   • corepressor
     • a small molecule that works together with the repressor to switch an operon off
   • activator
     • a protein that binds to DNA and stimulates transcription of a gene