It's harder to find one of the many genes involved in a polygenic trait vs the only gene involved in a discrete trait.
That would be cell division
MRNA transfers genetic information in the nucleus from the DNA to the cytoplasm because DNA never leaves the nucleus
If there was once a fish there then that would mean the habitat of a fish was once there but dried up. a lake or river or even an ocean could have once been there but dried up and left a fish fossil
