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June 3, 2022  

CHAPTER 34, HOW RETINAL LAYERS TRANSDUCE LIGHT.WHAT ELETROMAGNETIC AND SPECTRA ARE VISIBLE TO HUMAN EYE? WHAT GENETIC RELATIONS ARE IN LIGHT TRANSMISSION.

[ইংরেজীতে প্রকাশিত করা হল কিছু কিছু বাংলাদেশী বংশোদ্ভূত বিদেশে অবস্থানরত ছাত্র পাঠকেরা যারা বাংলা ভাষা পড়তে পারেনা, তাদের অনুরোধে, দুখিত]

Dear viewers,

It is written as a primary knowledge for the students who are interested in studying medical sciences. Today we are going to discuss about how retinal layers transduce light.

STRUCTURE OF RETINA

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FIGURE-1

 

SOURCE OF FIGURE  TEXT- https://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/

 

 Special Senses | The Photo transduction Cascade

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Special Senses | The Photo transduction Cascade

FIGURE 2

Special Senses | The Phototransduction Cascade – YouTube

The Electromagnetic and Visible Spectra TEXT

SOURCE OF TEXT LINK–  https://www.physicsclassroom.com/class/light/u12l2a.cfm

Light Waves and Color – Lesson 2 – Color and Vision

The Electromagnetic and Visible Spectra

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Figure-3

Visible Light Spectrum

The focus of Lesson 2 will be upon the visible light region – the very narrow band of wavelengths located to the right of the infrared region and to the left of the ultraviolet region. Though electromagnetic waves exist in a vast range of wavelengths, our eyes are sensitive to only a very narrow band. Since this narrow band of wavelengths is the means by which humans see, we refer to it as the visible light spectrum. Normally when we use the term “light,” we are referring to a type of electromagnetic wave that stimulates the retina of our eyes. In this sense, we are referring to visible light, a small spectrum from the enormous range of frequencies of electromagnetic radiation. This visible light region consists of a spectrum of wavelengths that range from approximately 700 nanometers (abbreviated nm) to approximately 400 nm. Expressed in more familiar units, the range of wavelengths extends from 7 x 10-7 meter to 4 x 10-7 meter. This narrow band of visible light is affectionately known as ROYGBIV.

Eye, how DNA acts on retina, chapter 26(6)

Link WordPress-   https://dnaandthemystryofhumanbody.wordpress.com/2017/05/26/eye-how-dna-acts-on-retina-chapter-266/

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Figure- 4

Source of figure-  http://www.nobelprize.org/nobel_prizes/medicine/laureates/1967/

The photos of the scientists (From left to right)-

1)Ragnar Granit

Born: 30 October 1900, Helsinki, Russian Empire (now Finland)

Died: 12 March 1991, Stockholm, Sweden

Affiliation at the time of the award: Karolinska Institutet, Stockholm, Sweden

2) Haldan Keffer Hartline

Born: 22 December 1903, Bloomsburg, PA, USA

Died: 17 March 1983, Fallston, MD, USA

Affiliation at the time of the award: Rockefeller University, New York, NY, USA

3) George Wald

Born: 18 November 1906, New York, NY, USA

Died: 12 April 1997, Cambridge, MA, USA

Affiliation at the time of the award: Harvard University, Cambridge, MA, USA

The above scientists-trio, working upon physiological and chemical matters of Retina, earned Nobel Award on Physiology or Medicine in 1967.(1)

How do the Rods and Cones transduce the light energy into electric energy and the Visual Center transduce the electric energy into a photo?

Yes, this transduction does not happen like magic. It needs to occur a complex chemical reaction over there to transduce. The light rays transduce into electric energy and transmits to the visual cortex and we can see the object, if the complex chemical reaction completes

What does complex chemical reaction occur there?

Like the harmful waste product produced in industry while production goes on, a chemical poisonous waste product named “N-retinylidene-PE “ is also produced inside the cell while the Rods and Cones cells transduce the light rays into electric energy.

If this poisonous waste product is not destroyed immediately, the Rods and Cones cell will be damaged soon and we will become blind.

Then what can you do now?

Yes, there is an arrangement to produce an antidote to destruct this poisonous chemical waste product immediately over there.

That antidote is produced by a gene named “ABCA4 “. This gene is always producing antidote that is destructing this waste product and keeps our vision always active or we would be blind soon.

The disease produced by mutation of this gene is called ‘Stargardt macular degeneration”.

Thus far 500 cases of such mutation have been found.(2) figure-2

Below is shown the location of gene “ABCA4”-

It is located at 22 of P arm in Chromosome no 1 in between base pairs  93,992,836  and 94,121,148

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Figure-5

Source of figure- http://ghr.nlm.nih.gov/gene/ABCA4

Besides this waste product, there are more waste product for which there are more genes also.

Below another gene named “ELOVL4” is also shown. It’s function is some different. It combines small fatty acids with carbon atom into long fatty acids.
But it is yet unclear what is the function of this long fatty acids.(3) figure-3

The location of ELOVL4 gene is at 14 of q arm in chromosome no 6, in between base pair 79,914,811 and 79,947,597

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Fig-6

Source of figure-http://ghr.nlm.nih.gov/gene/ELOVL4

DATE: 6/3/2022

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