How does histone acetylation affect chromatin?

a) it loosens the chromatin and allows increased transcription.
b) it allows dna to become resistant to damage.
c) it the histones have a greater affinity for dna.
d) it inhibits dna replication by making it more difficult to separate the dna strands.
e) it causes the chromatin to become more condensed in preparation for metaphase.

The correct answer is option A.

Explanation:

The histone acetylation catalyzed by histone acetyltransferases and deacetylation catalyzed by histone deacetylases performs a significant role in the regulation of the expression of genes in eukaryotes. Histone acetylation diminishes the affinity of histones towards DNA leading to relaxing or decondensation of chromatin and becomes accessible to the transcriptional apparatus and to perform transcription.  

It can be stated that histone acetylation is related to expression or gene or activation and histone deacetylation is related to the inactivation of gene or repression.  

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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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