The phenomenon of multiple allelism and co-dominance is shown by the ABO blood group in human beings. The gene I for the blood group contains three alleles i.e. I^A, I^B and i which represents the phenomenon of multiple allelism as it has more than two alleles governing the same character. The alleles I^A and I^B  are co-dominant and express themselves even in the presence of the other. Thus the presence of both the alleles I^A and I^B gives the blood group of AB.

The scientific name of the fruit-fly is - Drosophila melanogaster.

Morgan preferred to work with fruit-flies for his experiments because of the following reasons:

i. They could be grown on simple synthetic medium in the laboratory.

ii. They completed their life cycle in about two weeks and a single mating could produce a large number of progeny flies.

iii. It had many types of hereditary variations that could be seen with low power microscopes.

Linkage is the tendency for two or more non-allelic genes to be inherited together, because they are located more or less closely on the same chromosome.
Crossing over is the process by which two homologous chromosomes pair up and exchange sections of the coiled DNA.
If linkage is high the crossing over will be low.
If linkage is less the crossing over will be more. 

In Drosophila a yellow bodied white eyed female was crossed with brown bodied red eyed male, F1 progeny produced and intercrossed the F2 phenotypic ratio of Drosophila deviated significantly from Mendel’s 9:3:3:1, the genes for eye colour & body colour are closely located on the ‘X’ chromosome showing high linkage & therefore inherited together, recombinants were formed due to crossing over but at low percentage.

The symptoms of ascariasis include internal bleeding, muscular pain, fever, anemia and blockage of intestinal passage.

Nucleopolyhedro viruses play a significant role in an ecological sensitive area. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications. They have been shown to have no negative impacts on plants, mammals, birds, fish or even on non-target insects.