A mutation has occurred that results in a drastic reduction in mRNA transcription from very high levels to low levels. What region is likely responsible?

Enhancer region

Explanation:

An enhancer is a cis-regulatory DNA region that binds to transcription factors in order to stimulate transcription. Enhancer regions are localized both upstream and downstream of the gene whose transcription regulates, at a variable distance ranging from 1 to 100 kilobases (kb) from the transcription start site. The first enhancer to be identified was found in an intron of the immunoglobulin gene. Conversely, a silencer element is a DNA region that binds to proteins known as repressors in order to suppress transcription.

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