Identical twins have the same DNA but not always the same pattern of gene expression. Explain why this is in terms of epigenetics. How does epigenetics relate to transcriptional control of eukaryotic gene expression? Specifically describe the mechanisms which allow or prevent transcription.

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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burning fossil fouls really decrease the carbon in the atmosphere so b

yes we can.   a lady urinates from her urethra.