Q1. With reference to optogenetics, consider the following statements:
- It combines genetic modification with optical stimulation to selectively control the activity of particular cells.
- Channelrhodopsins are light-gated ion channels originally identified through studies of light-sensing mechanisms in microorganisms.
- Activation of Channelrhodopsin-2 can alter the electrical state of a neuron by allowing positively charged ions to enter the cell.
- Unlike conventional methods of studying neural activity, optogenetics can only record neuronal activity and cannot experimentally manipulate it.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 1, 2 and 3 only
(c) 2, 3 and 4 only
(d) 1, 2, 3 and 4
Answer: (b)
Explanation:
- Statement 1 is correct: Optogenetics involves introducing genes encoding light-sensitive proteins into selected cells and subsequently using light to control them.
- Statement 2 is correct: Channelrhodopsins are microbial opsins functioning as light-gated ion channels; their discovery emerged from studies of organisms such as Chlamydomonas.
- Statement 3 is correct: ChR2 opens upon illumination and permits positively charged ions to enter, changing the membrane potential and producing neuronal excitation.
- Statement 4 is incorrect: A major significance of optogenetics is precisely that it permits causal manipulation of selected neurons, rather than merely observing their activity.
