Final answer:
Steroid hormones can diffuse across the plasma membrane and bind to intracellular receptors, consequently altering the rate of mRNA transcription to regulate gene expression.
Step-by-step explanation:
Which statement is true regarding steroid hormones? The true statement is: D) They can alter the rate of mRNA transcription.
Steroid hormones are lipid-soluble molecules derived from cholesterol. They can easily diffuse across the plasma membrane of target cells. Once inside, these hormones bind to specific intracellular receptors located either in the cytoplasm or the nucleus.
The hormone-receptor complex then enters the nucleus, where it can act as a transcription regulator. This complex binds to specific DNA sequences, altering the rate of mRNA transcription, and consequently, protein synthesis. Therefore, steroid hormones can indeed regulate gene expression by modifying the amount of mRNA transcribed, which affects the synthesis of proteins that mediate the cell's activities and functions.