Linkage or crossing-over of genes are alternatives of each other.Justify with the help of an example

In Drosophila a yellow bodied white eyed female was crossed with brown bodies red eyed male,
${{F}{1}}$ progeny produced and inter crossed the ${{F}{2}}$ phenotypic ratio of Drosophila deviated significantly from Mendel’s 9:3:3:1, the genes for eye colour and body colour are closely located on the ‘X’ chromosome showing linkage and therefore inherited together, recombinants were formed due to crossing over but at low percentage.