Final answer:
Enhancers and repressors modulate gene expression through DNA binding and chromatin conformation changes, not by altering the genetic sequence itself.
Step-by-step explanation:
The mechanisms used by enhancers and repressors to affect gene expression include binding to specific sites on the DNA, such as promoter regions and enhancer elements, and altering the conformation of chromatin. Enhancers increase the efficiency of gene expression, while repressors prevent it by blocking the access of transcription factors to the DNA. However, changing the genetic sequence of the DNA itself is not a mechanism by which enhancers and repressors function; rather, they modulate the use of the genetic information without altering the actual genetic code.