In a molecule of RNA, the nitrogen-base A always pairs with , and G always pairs with .

In the space below, answer ONE of the following questions: Define passive transport and active transport, including any differences between them.  Water balance actually occurs at the cellular level, and maintaining the proper water balance is very important to an organism.    We see the results of this water movement in our daily lives.  Explain why your lettuce gets wilty when you pour vinegar-and-oil dressing on it (make sure to use the proper terminology).  Include the following in your answer:  water and solute concentrations, concentration gradients, type of solution, direction and mechanism of movement, and result to cells. OR Describe how a strand of DNA can eventually become a protein through the processes of transcription and translation.  Include the location of each of these processes, the main events of each, and the names and roles of each of the three types of RNA.  

Regardless of the number of alleles for a trait that exist in the population, the maximum number of alleles for a trait that a healthy individual can possess is .

Target cells closest to the signal-producing cell can have different responses than target cells further away in paracrine signaling.

Which of the following directly contributes to the refractory period in a neuron?

The 5′ UTR on an mRNA is defined by the position of the stop codon.

Eukaryotic mRNAs are monocistronic.

The four promoters above are identified as A-D. Match each promoter with the correct RNA polymerase.

Which of the following activities is not associated with post-translational processing of proteins?

Diffusion of molecules is not used at all in signaling via action potentials.