What is the difference between Allele and Gene?

A gene is a sequence of DNA that codes for a specific trait, for example eye colour. An allele is a very small variation the the sequence of bases in DNA that results in a variation of the physical outcome, as a result of mutation. For example, a typically brown eye colour might have a small mutation that wasn't expressed, but isin the offspring, resulting in a green eye colour, for example

Gene is a stretch of a DNA that determines a particular trait. Genescan mutate and take two or more alternative forms, now these are called alleles of a particular gene. Now allele occurs in a fixed spot in a chromosome and in humans we have two sets of chromosomes.