HW3

3) Enhancer is a short DNA sequence which can be a binding site for specific transcription factors - activators in order to increase the like probability that this gene will be transcripted. In other words, enhancer "enhances" the transcription of the gene.

The difference between enhances and promoters lies in very definition - the enhancers are used to amplify the transcription of gene, while promoter is used to initiate transcription. Also enhancer binds with transcription factors as activators, while promoter binds with general transcription factors (GTFs) and enzymes such as RNA polymerase. While enhancer can be located in upstream or downstream, the promoter needs to be located only upstream of gene. The finale difference is that the enhancer can be located in a relatively large distance from transcription site, while promoter needs to be located close to it.

4)In human organism there is approximately 2800 proteins with DNA-binding sides and only 1600 of them are presumed to be transcription factors (though other studies reveal the smaller number). Therefore the use of approximately 2000 human transcription factors can explain the complexity and uniqueness of regulation of each gene during the development.