Alleles of different genes that are on the same chromosome may occasionally be separated by a phenomenon known as

If the gene exchange rate (recombination frequency) of two linked genes is $30\%$,then the distance between these two genes is:

Give differences: Crossing over and Linkage.

The following experiment is the result of a dihybrid cross performed by Morgan. Identify the proportions of $P, Q, R,$ and $S$.

The linkage map of $X$-chromosome of fruit fly has $66$ units with yellow body gene $(y)$ at one end and bobbed hair $(b)$ gene at the other end. The recombination frequency between these two genes ($y$ and $b$) should be

What happens in the process of variation?