Why do we study mutations of karyotypes? what information do they give us?

Karyotype testing can be done using almost any cell or tissue from the body. A karyotype test usually is done on a blood sample taken from a vein. For testing during pregnancy, it may also be done on a sample of amniotic fluid or the placenta

A regular human cell has 46 chromosomes: 44 autosomes, which come in pairs, and 2 sex chromosomes, which specify whether someone is male (usually XY) or female (usually XX). The pairs of autosomes are called "homologous chromosomes

it can tell you if you have ricks or if you have a disorder or if you are a carrier

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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b. lithosphere, asthenosphere, mesosphere   is the answer most likely