Final answer:
The enhancer sequence functions in a cell are limited by the formation of DNA loops, which bring enhancers and specific gene promoters into close proximity for effective transcription regulation.
Step-by-step explanation:
In the cell, enhancer sequence functions are limited in their range of action by the formation of loops that hold specific genes and enhancers in close proximity. The correct answer is A. loops.
Enhancer sequences are critical in regulating gene expression. Even though these sequences can be located far from the promoter region of a gene, DNA loops bring the enhancer into close proximity with the promoter. This three-dimensional configuration allows transcription factors and activators bound to the enhancer to interact effectively with the mediator proteins and general transcription factors that are bound to the promoter region, facilitating transcription.