Self And The Phenomenon Of Life: A Biologist Examines Life From Molecules To Humanity

348 Self and the Phenomenon of Life

b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”

protein into the genome. A neuron emits light and becomes visible when

it is active. (2) Optogenetic stimulation consists of incorporating a light

sensitive protein into the genome so that the neuron can be switched

“on” or “off” by a beam of light into a moving animal through a tiny fiber

optic. Depending on the choice of protein that affects the ion channel

of a cell membrane, the light sensor can either activate or suppress the

activity of a neuron. By engineering the protein to respond to light of

a particular wavelength, neurons of different types can be simultane-

ously manipulated to reveal their interaction. By targeting the foreign

gene to a selected neuronal population or part of the nervous system, the

method bypasses the tedious transgenic and knock-in/knockout proce-

dures. Its simplicity and incomparably high resolution in time and space

surpass those of electrophysiology, making it by far the most promising

of all micro-manipulative approaches.

Rapid gene editing using CRISPR system — CRISPR is a bacte-

rial defense mechanism against viral infection in which a variable RNA

target sequence is joined to a constant CRISPR sequence. The target

sequence binds to specific target DNA segment while the constant

CRISPR RNA sequence recruits an enzyme (nuclease) that cleaves the

DNA site. When applied to animal cells, the system permits the spe-

cific cutting of a DNA molecule and the introduction of a foreign DNA

segment, making possible gene editing with unprecedented speed and

ease. This novel approach holds great promise for the study of neuronal

functions.

Behavioral studies

Ethology deals with observing animal behavior in their natural habitat,

and has led to such interesting findings as imprinting in newly hatched

goslings. Animal training is a way to study classical and operant con-

ditionings. The latter involves the active participation of the animal

under positive or negative reinforcement. Studies of space memory can

be carried out in a Morris water maze or a Barnes maze. Human

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