The chromosomal theory of inheritance was proposed by

Walter Sutton and Theodor Boveri independently proposed the chromosomal theory of inheritance in the early 20th century. Their work emphasised the role of chromosomes in heredity and how the behaviour of chromosomes during meiosis explains Mendelian patterns of inheritance.

(1) Thomas Morgan is well known for his work on fruit flies (Drosophila melanogaster) and his discoveries 
related  to sex-linked inheritance, which further supported and experimentally proved the chromosomal theory of inheritance.
(3) Gregor Mendel formulated the fundamental principles of inheritance through his experiments with pea plants.

(4) Robert Brown is credited with the discovery of the cell nucleus.