Molecular Basis of Inheritance neet The term gene was introduced by Johanssen in 1909. $>$ Prior to him Mendel used the word factor for a specific, distinct, particulate unit of inheritance. $>$ Johanssen has defined gene as an elementary unit of inheritance which can be assigned to a particular trait. Molecular Basis of Inheritance neet > Morgan's work suggested gene to be the shortest segment of chromosome which Can be separated through crossing over. Can undergo mutation. Influence expression of one or more traits. Molecular Basis of Inheritance neet 8 > Presently, a gene is defined as a unit of inheritance composed of a segment of DNA or chromosome situated at a specific locus (gene locus). $>$ It carries coded information associated with a specific function and can undergo of Crossing over. o Mutation.