Frequency of crossing over in a chromosome is an index of

In maize plants,genes $R$ and $y$ are located very close to each other on the chromosome map. When a cross is made between $RRYY$ and $rryy$ genotypes,what will the $F_2$ analysis show?

Crossing over in a diploid organism is responsible for

If $F_2$ of a dihybrid cross contains only parental combinations,then Mendel would have discovered .....

In $Drosophila$,long wing and broad abdomen characters are dominant over vestigial wing and narrow abdomen characters. $A$ pure-breeding $Drosophila$ with long wings and broad abdomen is crossed with a pure-breeding vestigial-winged and narrow-abdomened $Drosophila$. Two of the $F_1$ individuals were crossed,and the following results were produced in the $F_2$ generation: $482$ $Drosophila$ with long wings and broad abdomen,and $154$ $Drosophila$ with vestigial wings and narrow abdomen. Which one of the following is illustrated by these results?

Who coined the term 'linkage'?