In diploid organisms,crossing over is responsible for which of the following?

What is the result of linkage and crossing over?

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

The recombination frequency between the genes $a$ and $c$ is $5\%$,$b$ and $c$ is $15\%$,$b$ and $d$ is $9\%$,$a$ and $b$ is $20\%$,$c$ and $d$ is $24\%$,and $a$ and $d$ is $29\%$. What will be the sequence of these genes on a linear chromosome?

For the preparation of genetic maps,the recombination frequencies between genes are additive over short distances but not over long distances due to

Sex linkage was first observed by.....