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

Give scientific reasons : Linkage and crossing over of genes are alternatives of each other.
 

Genetic map is one that

Linkage in Drosophila was first discovered by

$A$ : Morgan's cross III was conducted in Drosophila to locate genes on chromosome for white eye colour.
$R$ : The cross was done between red eyed hybrid female and white eyed male.