the only answers to the eye, are blanket statements of this evolved to that. No scientist anywhere has discovered a chemical pathway from nothing to a photoreceptor. That was my only question. Nothing to do with the eye. Please keep your replies specific to the topic or it will get very confusing.
How does mutation get to the photoreceptor? no one knows, it is just excepted and expected. That is not the science you would let an ID'r use for proof.
If all you're seeking is how a photoreceptor could arise in an organism without photoreceptors, then the answer is one that you'll probably find a bit trite - mutation.
This may seem like a copout, but I'm unclear what more you're searching for. Let's look at a photoreceptor protein. The one I've picked is the Photoactive Yellow Protein PYP. It's a protein found in the bacterium Halorhodospira halophila that repsonds to blue light (meaning that it looks yellow - the blue light is absorbed rather than reflected). Here's the sequence of the protein. Each letter stands for an amino acid residue, the building blocks of proteins, and this shows you the order they fit together to make this particular protein:
MEHVAFGSEDIENTLAKMDDGQLDGLAFGAIQLDGDGNILQYNAAEGDITGRDPKQVIGK
NFFKDVAPCTDSPEFYGKFKEGVASGNLNTMFEYTFDYQMTPTKVKVHMKKALSGDSYWV
FVKRV
Now, there are any number of ways an organism could build this protein, since the genetic code is full of synonyms. For example, the protein sequence above starts with Methionine (M), then Glutamic Acid (E), then Histidine (H). The sequence of DNA coding for this bit in H. halophila is 'ATGGAACAC' (where each letter stands for one of the four nucleic bases which make up DNA), but exactly the same protein would be produced if it instead started 'ATGGAACAT', for example, or 'ATGGAGCAC'.
It also wouldn't need to be exactly the same protein. There are many different photoreceptor proteins found in nature, and there are probably many more that could potentially work, but which we don't see around us.
The basic point is that there are many different ways for a photoreceptor protein to appear. There are many different potential proteins, and many different ways to code for each specific protein. What, exactly, are you looking for here?
Edited by caffeine, : ABE: changed sub-topic
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