The number of linkage groups in $E. coli$ is:

The presence of recombinants is due to.....

Morgan and his group observed that when genes are grouped on the same chromosome,some genes are very tightly linked and show:

The evidence that crossing over occurs at the four-stranded stage and not at the two-stranded stage of the chromosomes comes from:

In which of the following is the phenomenon of crossing over $NOT$ observed?

The linkage map of a fruit fly has a total map distance of $66$ units. The gene for yellow body $(a)$ is at one end and the gene for short hair $(y)$ is at the other end. What will be the recombination frequency between these two genes $(a$ and $y)$?