How is it possible that regions thousands of base pairs from a promoter can impact transcription of that gene?
a. dna is capable of looping, bringing distant regions in the same proximity. b. proteins can be very large molecules, much larger than a nucleotide. c. transcription factors work in complexes, creating large chains of proteins.

A. DNA is capable of looping, bringing distant regions in the same proximity.

Explanation:

Transcriptional factors (such as activators or repressors) are proteins that regulate gene expression by binding to DNA sequence (such as enhancers and silencers). Consequently, gene transcription might be turned on or off. Usually binding sites for transcriptional factors are located near the promoter (initiation of transcription). But when they are located far from the gene they regulate DNA, flexibility plays a role. DNA can form loops which bring together binding sites and transcription factors.

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms