Why is impossible for post-transcriptional editing of mRNA to occur in prokaryotes?

It's impossible because there is no place within the cell for it to occur. In eukaryotes, you have two different regions; the nucleus and the cytoplasm. In prokaryotes, however, you lack the nucleus, meaning you only have the cytoplasm. So, as one can see, there is no separate region for post-transcriptional editing of mRNA to occur in prokaryotes.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.