•  The sex or germ cells (i.e., sperm and egg) appeared to have exactly half of the number of chromosomes as were found in the non‑germ or somatic cells of any organism. Furthermore, the germ cells were shown to have just one copy of each chromosome type. Such cells are called haploid cells. •   The fertilization of an egg with a sperm cell produces a diploid cell called a zygote, which has the same number of chromosomes as the somatic cells of that organism. •  Further they went on to show that in drosophila male gamates carried a Y chromosome while females carried an X chromosome.   Females were found to be XX while males are XY.  This assigned a specific trait to inheritance of a specific chromosome.  Chromosomes now became the target for carrying the genetic material.