Thomas Hunt Morgan work with the fruit fly showed that genes are linked in a series on chromosomes and are responsible for identifiable, hereditary traits. He was the first to identify that genes are linked to the same chromosome.
According to his hypothesis he stated that genes that are linked are arranged linearly on a chromosome, while those genes with low combination frequencies must be closer together and thus difficult to separate.
When a gene contains two similar alleles that is, either two dominant alleles or two recessive alleles then it is called homozygous dominant and homozygous recessive respectively. White eyes of a fruit fly is an example of homozygous recessive
