How is mitochondrial DNA (mtDNA) typing used in forensic science? An unknown mtDNA sample is matched to a sample of nuclear DNA that was found at a crime scene.
An unknown mtDNA sample is matched to a sample of mtDNA that was found at a crime scene.
An unknown nuclear DNA sample is matched to a sample of nuclear DNA that was found at a crime scene.
An unknown nuclear DNA sample is matched to a sample of mtDNA that was found at a crime scene.

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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unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.

well the answer is 2!

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d.  

there was a variety of food available on island x, but there were only large seeds and nuts on island y.