In the context of methods for analyzing DNA and gene expression, what is a reporter gene?

• A. A gene that encodes a DNA polymerase used to amplify DNA during PCR
• B. A gene that increases the mutation rate in a target locus to speed up genetic mapping
• C. A gene that directly repairs DNA double-strand breaks by homologous recombination
• D. A gene that encodes an easily measurable product (e.g., fluorescence or enzyme activity) used to monitor the activity of a regulatory sequence or expression of another gene

Answer: (D)

Verified step by step guidance

1. Understand that a reporter gene is a tool used in molecular biology to study gene expression and regulation.
2. Recognize that reporter genes encode products that are easy to detect and measure, such as fluorescent proteins or enzymes that produce a color change.
3. Know that these genes are linked to regulatory sequences or genes of interest, so their expression reflects the activity of those sequences or genes.
4. Realize that by measuring the reporter gene's product, scientists can infer when, where, and how strongly a gene is being expressed.
5. Conclude that a reporter gene is not involved in DNA amplification, mutation rate alteration, or DNA repair, but rather serves as a measurable indicator of gene expression.