Here is what I found, its quite interesting, I hope it helps..
https://www.fbi.gov/services/laboratory/biometric-analysis/codis/codis-and-ndis-fact-sheet
No they cant be mechanical because then something would have to generate their rays through the inventing of a machine.
Answer:
Gene. A segment of a DNA molecule (a sequence of bases) that codes for a particular protein and determines the traits (phenotype) of the individual. A gene is the basic unit of heredity in a living organism.
Question/Purpose
research
Hypothesis
Experiment
collect data and analyze
Conclusion
