Signal transduction is the process by which:

a. transcription factors bind to cis-regulatory regions of DNA and either activate or repress transcription.

b. None of the answer options is correct.

c. an extracellular molecule activates a membrane protein, which in turn activates molecules inside the cell.

d. a single master gene, or signal, activates a series of downstream genes that lead to cell differentiation.

e. a specific combination of transcription factors determines the developmental pathway in a cell or group of cells

An extracellular molecule activates a membrane protein, which in turn activates molecules inside the cell.

Explanation:

Signal transduction may be defined as the cellular process in which the signal is transmitted into the cells. The signal transduction results in the detection of the stimuli and the effects generated in the body.

The signal transduction initiates the series of cascade for the signal transmission. The protein is activated by the extracellular molecule and activates the different molecules by the phosphorylation at the different steps of the transduction.

Thus, the correct answer is option (c).