In the construction of chromosome maps,the evidence is derived mainly from

Genes $p, q,$ and $r$ are arranged on a chromosome. If the recombination frequency between $p$ and $q$ is $10 \%$,the recombination frequency between $q$ and $r$ is $20 \%$,and the recombination frequency between $p$ and $r$ is $10 \%$,what is the order of the genes on the chromosome?

There are three genes $a, b, c$ with percentage of crossing over between $a$ and $b$ is $20\%$,$b$ and $c$ is $28\%$,and $a$ and $c$ is $8\%$. What is the sequence of genes on the chromosome?

If interference is complete or $100\%$ then the frequency of observed double crossover will be:

The first attempt to demonstrate linkage in plants was made in $.....$.

Mendel did not recognize the linkage phenomenon in his experiments because