The chromosomal theory of Heridity explains

The chromosomal theory of Heredity explains Genes are located on chromosomes and transmitted to the next generation through them.
The Boveri-Sutton chromosome theory is a fundamental unifying theory of genetics that identifies chromosomes as the carriers of genetic material.
It states simply that chromosomes, which are seen in all dividing cells and pass from one generation to the next, are the basis for all genetic inheritance.