What are the three mechanisms by which transcription factors regulate eukaryotic gene expression

1.       They act as activators of transcription. This is through increasing the affinity of the RNA polymerase on the promoter

2.       They could act as repressors. This way, when they bind to their active sites, they repress the binding of the RNA polymerase on the promoter

3.        Transcription factors at one site could affect transcription of genes on another site on the DNA. The flexibility of the DNA (by forming loops) allows for this phenomenon.

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.