Final answer:
The central idea in genetics is that genetic information usually flows from DNA to mRNA to protein.
Step-by-step explanation:
The central idea in genetics is that genetic information usually flows from DNA to mRNA to protein. This concept is known as the central dogma of molecular biology. It describes the process by which genes specify the sequences of mRNA, which in turn specify the sequences of proteins. The flow of genetic information from DNA to mRNA to protein is essential for the functioning and development of organisms.