Answer:
There are histones in the nucleus that DNA coils around. The part of the DNA that is coiled around the histones is not accessible, and cannot be expressed in that cell. DNA that is not wrapped around a histone can be transcribed.
Explanation:
<span>transcription/RNA processing-
pre-mRNA, mRNA, snRNA
translation- rRNA, tRNA</span>
Small, electron-lucent vesicles known as synaptic vesicles (SVs) are grouped at presynaptic terminals. They hold neurotransmitters and exocytosis, which is stimulated by calcium, releases them. After exocytosis, SVs are formed locally at the terminals.
- From the presynaptic cell with synaptic vesicles to the postsynaptic cell with neurotransmitter receptors, a signal always moves in one direction across the chemical synapse.
- The correct routing of nerve signals throughout the body is guaranteed by this one-way communication.
- A signal is transmitted from one neuron—the presynaptic, or sending, neuron—to another neuron—the postsynaptic, or receiving, neuron—at the synapse, increasing or decreasing the likelihood that the postsynaptic neuron will fire its own action potential.
- The stimulation causes a sensory neuron to go into an action potential, which alters the motor neuron's potential.
- Excitatory because it tends to depolarize the cell, this potential is known as an excitatory postsynaptic potential (EPSP).
learn more about synaptic vesicles here:brainly.com/question/5865840
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In my opinion
Mass extinctions happen because of climate change, asteroid impacts, massive volcanic eruptions or a combination of these causes. One famous mass extinction event is the one that lead to the extinction of dinosaurs, 65 million years ago.
I hope it’s help
