In what stage of meiosis is crossing over most likely to occur?
a. prophase i
b. anaphase ii
c. metaphase i
d. prophase ii

Option A, Prophase I

Explanation:

It is during the prophase I stage of meiosis when chromatic tetrads exchange their chromosomes followed by disappearance of  nucleus envelope.

In Meta phase I,  the chromatic tetrads arrange themselves along the equator.

In Anaphase II, sister chromatids (within each chromosomes) seperate from each other and move towards the opposite end of the cell.

In Prophase II, haploid cells formed in meiosis I condenses their chromosomes.

Hence, option A is correct.

dna damages cause changes in the structure of the genetic material and prevents the replication mechanism from functioning and performing properly. dna damage and mutation have different biological consequences. while most dna damages can undergo dna repair, such repair is not 100% efficient.

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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