a branch of biology that studies the chemical and physical principles associated with the composition, properties, and activities of molecules in living cells
See molecular biology in American Heritage Dictionary 4
noun
The branch of biology that deals with the formation, structure, and function of macromolecules essential to life, such as nucleic acids and proteins, and especially with their role in cell replication and the transmission of genetic information.
The branch of biology that deals with the manipulation of DNA so that it can be sequenced or mutated. If mutated, the DNA is often inserted into the genome of an organism to study the biological effects of the mutation.