Answer:
A sleepy driver rounds a bend and sees a deer standing in the road. The driver snaps to attention and applies the brakes, averting the accident, because his brain was aroused by the <u> Reticular Activating system(RAS).</u>
<u>Explanation:</u>
- Reticular activating system (RAS) is a part of brain that filters the sensory signal that tries to reach our brain.
- However the olfactory Signal do not pass through it .
- Reticular activating system is located at the brain stem little above the spinal column.
- This is an extremely important part of the brain because it sorts various sensory signals into important and non-important ones.
- RAS allows only those information into the brain that needs immediate attention of the conscious mind.
- Hence it is responsible for sudden wakefulness.
- Our sensory organs perceive thousands of information each second and direct them towards the brain.
- If RAS was not there then our brain would have reached a state of confusion every minute and might have failed to give proper response to any of the stimulus.
- In the given situation, the sudden sight of the deer acted as a threatening stimulus.
- This information needed immediate attention of the driver's conscious mind and his brain was thus aroused by the RAS.
Answer:
At the microscopic level of a visceral muscle cell are actin and myosin filaments. They slide past each other in an antiparallel manner to shorten the distances between their ends. In a smooth muscle cell, the ends of chains of these functional units are attached to the cell membrane. They are several in a cell arranged in an elaborate framework. They contract together and deferentially to enable the muscle to contract as needed.
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Answer:
No, there are multiple ways in which different mutations in the same gene can cause the same phenotype
Explanation:
Several different mechanisms of mutation can lead to the same phenotype. For example, lets say our phenotype is that flies have white eyes, and we know that this occurs in one particular gene that normally makes the eye colour red. (the red gene)
These mutations likely rendered the red gene ineffective (as the eyes are not red). However, this could happen in a variety of ways.
- There could be a single base deletion in the first exon of the mRNA, changing the reading frame of the protein and messing up the entire sequence (a frame shift mutations)
- The entire gene could be deleted
- A single base could be substituted in an important site of the gene, for example, one which translates into a catalytic residue or binding site in the protein
- There could be an inversion at the promoter region of the gene, such that a transcription factor can no longer bind to transcribe the gene.
There are countless other ways in which a mutation could have been caused. Therefore, just because we know the same gene is affected does not mean that we can assume the mutations are identical.
