How many linkage groups are present in Drosophila?

When a group of genes exhibits linkage,they:

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 $\%$)?

When linked characters or genes are inherited together through two or more generations,it is called

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?

Genes which are located on the same chromosome are