Explain the mechanism of haplo-diploid pattern of sex determination with the help of a suitable example. Why is this pattern so called ? OR T.S. Morgan and his colleagues worked with Drosophila melanogaster for their experiments. State the findings they arrived at and explain how.

Honey bee shows mechanism of haplo-diploid pattern of sex-determination, female (queen or worker) develops from fertilized egg, so are diploid, males (drones) develop from unfertilized egg by parthenogenesis, so are haploid, Females are diploid having $\displaystyle 32$ chromosomes and the males are haploid having $\displaystyle 16$ chromosomes this is haplo-diploid sex determinationIn a dihybrid cross the F2 phenotypic ration deviated very significantly from $\displaystyle 9$:$\displaystyle 3$:$\displaystyle 3$:$\displaystyle 1$, the proportion of the parental gene combination was much higher than the non-parental type, the parental combinations were due to linkage of genes (physical association) and the non-parental types were due to distant genes (recombination/ crossing over) (Explanation of the same if provided through cross should be considered)