Linked genes show.....

Who clearly proved and defined linkage?

The phenomenon that acts against linkage is......

Which of the following is an exception to Mendel's laws?

In a fruit fly,the $X$-chromosome linkage map has a total length of $66$ units,with the yellow body gene $(y)$ at one end and the bobbed hair gene $(b)$ at the other end. What will be the recombination frequency between these two genes $(y$ and $b)$?

Mendel observed that some characters did not assort independently. Later researchers found it to be due to