In the construction of chromosome maps,the evidence is derived mainly from

In $Lathyrus$ $odoratus$,a hybrid blue-flowered and long-pollen plant is test-crossed with a homozygous recessive red-flowered and round-pollen plant. How many parental types are obtained when genes are present in the $cis$ stage in parents (in $\%$)?

Drosophila has four pairs of chromosomes. How many linkage groups does it have?

Coupling and repulsion are the two faces of

Drosophila melanogaster has $8$ chromosomes in its somatic cell. How many linkage groups will it have?

When two genes are situated very close to each other in a chromosome,