An allele is a variant form of a gene. Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome. Humans are called diploid organisms because they have two alleles at each genetic locus, with one allele inherited from each parent.
Molecular nitrogen has to be fixed in order to be in the soil. This is achieved by living organisms or lightning naturally or man can fix nitrogen in the process of making fertilizer.
