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It has also been identified in other places such as the heart, and in aggressive breast cancer tumors. [2] [3] The physical origins of eye lens transparency and its relationship to cataract are an active area of research. [4] Since it has been shown that lens injury may promote nerve regeneration, [5] crystallin has been an area of neural research.
Rhodopsin is a protein found in the outer segment discs of rod cells. It mediates scotopic vision , which is monochromatic vision in dim light. [ 7 ] [ 19 ] Rhodopsin most strongly absorbs green-blue light (~500 nm) [ 20 ] [ 21 ] and appears therefore reddish-purple, hence the archaic term "visual purple".
The seven transmembrane α-helical domains in opsins are connected by three extra-cellular and three cytoplasmic loops. Along the α-helices and the loops, many amino acid residues are highly conserved between all opsin groups, indicating that they serve important functions and thus are called functionally conserved residues.
The polymorphisms may be in an OCA2 regulatory sequence, where they may influence the expression of the gene product, which in turn affects pigmentation. [13] A specific mutation within the HERC2 gene, a gene that regulates OCA2 expression, is partly responsible for blue eyes. [9] Other genes implicated in eye color variation are SLC24A4 [22 ...
Additionally, the genetic toolkit for positioning eyes is shared by all animals: The PAX6 gene controls where eyes develop in animals ranging from octopuses [17] to mice and fruit flies. [ 18 ] [ 19 ] [ 20 ] Such high-level genes are, by implication, much older than many of the structures that they control today; they must originally have ...
The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction.The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes.
Several layers such as the neural tube, neural crest, surface ectoderm, and mesoderm contribute to the development of the eye. [2] [3] [4] Eye development is initiated by the master control gene PAX6, a homeobox gene with known homologues in humans (aniridia), mice (small eye), and Drosophila (eyeless). The PAX6 gene locus is a transcription ...