This is one of our sample questions for the exam of molecular biology and geneti

Question

This is one of our sample questions for the exam of molecular biology and genetics. It would be very kind of you if you write the answer and its explanation as clearly as possible.

Q1)The figure shows the MRI images of (a) 27 year old healthy male, (b) 27 year old male with first- episode psychosis, (c) 25 year old male with chronic schizophrenia brains. The white color corresponds to myelinated axons. t has been shown that the decrease in myelination is statistically correlated with the onset of schizophrenia. Speculate on the mechanism of the disease by referring to the functions of myelination. (9pts.)

Explanation / Answer

Axons of nerve fibres are surrounded by a fatty white substances which acts as an electrically insulated layer. The production of myelin sheath is essential for the normal functioning of the nervous system and the process itself is termed as myelination or myelinogenesis. The Myelin sheath is a protective covering of axon and enhance their electrical impulse transmission.

During the process of demyelination the electrical impulses are not conducted properly across the nerve fibres. It may also end up in damage to the nerve fibres. When the myelin sheath is damaged the efficiency of nerve fibre in conducting impulse become very less as a result of which the information from the brain to the body or from the body to the brain is not properly processed.

As this condition persist it may lead to state known as psychosis, where the thoughts and emotions are lost and are disconnected from the reality.

As we can see from the image of MRI scan, that the (a.) 27 year old healthy subject has more number of myelinated nerve fibres across the brain. Whereas in the (b.) 27 year old subject with the first episode of psychosis we could observe a change in the amount of myelin sheath. As we could we see the amount of white colour has decreased which implies demyelination has occurred in the nerve fibre which lead to a condition known as psychosis.

But in the image (c.) A severe condition is observed where the amount of myelin sheath covering is very very less. It seems to be a very chronic conditions where all the myelin sheath has been destroyed or damaged. It is observed in schizophrenia patient.

More evidence suggests that myelin dysfunction is associated with schizophrenia. Myelin dysfunction is schizophrenia subject has lead to changes in synaptic formation and function. This condition leads to cognitive dysfunction which is a core symptom in schizophrenia. It's also found that in schizophrenia patients myelin dysfunction is associated with dopamine and glutamate abnormalities, these are the neurotransmitter which are responsible for feelings and emotions.

So approach or strategies targetting the myelin abnormalities can pave way for the treatment of schizophrenia. Even gene involved in myelin formation can also be trangetted in case the disorders was inherited.

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