You are studying the expression of the gene that appears to be under the control of three different transcription-control regions during mouse embryonic development. which one of the following is the best method to use to determine when each of these regions are active in the developing mouse embryo?
a - dna affinity chromatography
b - polymerase chain reaction
c - dnase i footprinting
d - reporter gene assay

The correct answer is option D, that is, reporter gene assay.  

Explanation:

A reporter gene in molecular biology refers to a gene, which the scientists combine with a regulatory sequence of another gene of interest in cell culture, bacteria, plants, or animals. In the given case, reporter gene assay is the appropriate approach as a reporter gene can get combined with the gene of interest and can help in determining the active region.  

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