1. The genetic code is different in nearly all organisms
2. Cells regulate gene expression so that each gene will betranscribed only when it is needed.
3. Gene expression is prevented when a repressor binds tothe group of genes involved in the same function.
4. Repressor proteins are bound to the DNA in front of eachgene, readily allowing transcription to take place as the RNApolymerase moves along that gene.