Help with Chromosomes and eye color!?

How did Morgan determine that eye color in Drosophilia is an X-linked trait?Help with Chromosomes and eye color!?
T.H.Morgan made different crosses as follows.





Cross I





Red eyed female * white eyed male ===飪?F1 progeny with only red eyed females and males.





Then he crossed red eyed males of F1 with red eyed females of F1 progeny.


Results 鈥?br>

-all F2 females were red eyed.


-half of F2 males were red eyed.


-half of F2 males white eyed.


-the mendalian ratio of total red to total white offsrings was still 3:1.











Cross II





F1 red eyed females with white eyed males.=飪?red and white females and males were produced in an equal proportion . it led to conclude that white eye color is not restricted to male sex.











Cross III





White eyed female with red eyed male ===飪?all males white eyed and all females red eyed.














All these above results showed that inheritance of eye color is somehow related to sex. Since the male flies showed the white eyed ( a recessive trait) much more frequently than the females, it suggested that this recessive (white) allele was present on the X chromosome and the Y chromosome did not have its corresponding allele.





Hence, morgan concluded that only the X chromosome carried the gene for eye color. Y chromosome did not have the gene locus for eye color.


The genes like the eye color in Drosophila which are carried on the sex chromosomes are said to be X-linked inheritance.