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

When the number of recombinant progeny is usually less than the number expected in independent assortment, it is called:

As the length of the chromosome increases in an organism,which of the following increases?

Genes on the same chromosome can be:

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?

Crossing over is