When scientists clone a gene, they isolate and make exact copies of just one of an organism's genes. Cloning a gene usually involves copying the DNA sequence of that gene into a smaller, more easily manipulated piece of DNA, such as a plasmid. This process makes it easier to study the function of the individual gene in the laboratory.
To me a deep thinker is someone who is an innately curious, and deeply insightful. He/she has a profound understanding of the right questions to ask in the face of both reality and the unknown. He/she is not afraid to see reality and what is there before him/her.
Do you see things other people don't? The fact that other people may think you're slow because your mind is elsewhere is irrelevant. That is, it has no bearing upon whether you are a deep thinker or not. Finally, I'd have to answer yes: deep thinkers are serious, but there's a difference between being serious and lacking a sense of humour.