Molecular genetics is a subdivision of biology that addresses how differences in the structures or expression of DNA molecules manifests as variation among organisms. Molecular genetics frequently applies an "investigative approach" to determine the structure and/or function of genes in an organism's genome using genetic screens. The field of study is based on the combination of several sub-fields in biology: classical Mendelian inheritance, cellular biology, molecular biology, biochemistry, and biotechnology.
Neurobiology is the study of the nervous system and how the brain works. The field studies nervous system functions, brain function and the related structures such as the spinal cord. Neurobiology is a subcategory of both neuroscience and physiology. It is a sub discipline of the life sciences that handles with the anatomy, pathology and physiology of the nervous system.