Before Mendel
(according to Francis Galton, 1822 - 1911):
Mendel's principle of inheritance
(1865):
combination of autosomal genes
1916, X/Y - chromosomal inheritance
was discovered
(Th. H. Morgan / Calvin B. Bridges)
Sex is determined by the male sperm
cell. The Mendelian laws are modified in respect to the inheritance
of the sex chromosomes (X,Y) by this particular male position.
Because of the limitations set by the gender, there
are only 4 possible combinations of X/Y chromosomes : No
sons carrying the paternal X1, and no daughters carrying
the paternal Y0 !
