If a dominant allele for tallness is expressed as t and a recessive allele for shortness is expressed as t, what is the genotype: for a heterozygous dominant pair of chromosomes?

Heterozygous dominant genotype would be Tt

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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explanation:

on disadvantage of hydroelectric power is the cost. another disadvantage of using hydroelectric power is finding a water source powerful enough to harvest hydroelectric power.