Which statement best describes how DNA specifies a genetic trait? A) The four nitrogenous bases of DNA nucleotides always form the same base
pairs.
B) The order of nitrogenous bases in DNA determines the order of amino acids in
proteins.
C) One strand of a DNA molecule serves as a template for making the other
strand.
D) DNA molecules are copied before cell division in the process of DNA replication.

1. beginning with all chambers of the heart in the "relaxed" phase, describe the cardiac cycle in mammals, with systole and diastole of the atria and ventricles. for each time point in the cycle you select, state the following: • whether the atria and ventricles are contracting or relaxing • whether the av valves and semilunar valves are closed or open • whether the pressure in the atria and ventricles is high or low