Who clearly proved and defined linkage?

The recombination frequency between genes $B$ and $A$ is $5\%$. The recombination frequency between genes $A$ and $C$ is $15\%$. What is the possible sequence of these genes on the chromosome?

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

Two genes $R$ and $Y$ are located very close on the chromosomal linkage map of maize plant. When $RRYY$ and $rryy$ genotypes are hybridized,then $F_{2}$-segregation will show:

In maize, colored endosperm $(C)$ is dominant over colorless $(c)$ and full endosperm $(R)$ is dominant over shrunken $(r)$. When a test cross is performed on the $F_1$ generation, the following results are obtained:
Colored and Full = $45\%$
Colored and Shrunken = $5\%$
Colorless and Full = $4\%$
Colorless and Shrunken = $46\%$
Based on this data, what is the distance between the two non-allelic genes (in $units$)?

The frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes was explained by