It is also known that activated PKA phosphorylates the transcriptional regulator called Nerd that then activates transcription of the gene Brainy. For each of the following conditions, describe the impact on Brainy transcription following stimulation with adrenaline. Explain your reasoning. A. A mutation in the Nerd gene that produces a protein that cannot be phosphorylated by PKA. B. A mutation in the nuclear import sequence of PKA from PPKKKRKV to PPV. C. A mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive. D. A mutation in the gene that encodes adenylyl cyclase that renders the enzyme unable to interact with the alpha subunit of the G protein.