Linkage decreases the frequency of

In a somatic cell,if the arrangement of genes is such that dominant alleles are present on one chromosome and recessive alleles are present on the other chromosome of a homologous pair,what is this arrangement called?

What is the result of linkage and crossing over?

The phenomenon of crossing over in diploid organisms is responsible for

Thomas Hunt Morgan and his colleagues performed experiments on which organism to verify the chromosomal theory of inheritance and later demonstrated linkage?

In a test cross involving $F_1$ dihybrid flies,more parental-type offspring were produced than the recombinant-type offspring. This indicates