Answer:
according to me the answer is abiotic factor
The allele which has light color appears to be altering transcription and that is why the corresponding mRNA is absent in zebrafish which is homozygous. The protein we can say were absent because mRNA which is being required for protein synthesis it was not present.
If the allele had altered translation, mRNA which is functional would have been present but in the same case, the protein will still be absent.
The arrangement of specialized parts within a living thing is sometimes referred to as levels of organization. Cells, of course, are the first level of organization. In any multicellular organism, cells rarely work alone. Cells that are similar in structure and function are usually joined together to form tissues.
