Thomas Morgan, studied the phenomenon of heredity on the prolific fly-Drosophila. The object was very successful: a short development period (10-12 days), very fertile, easy to breed artificially on nutrient media, a small number of chromosomes 2n = 8. Morgan analyzed a large number of signs in Drosophila: color and shape of the body, length of wings, eye color, and many others. It turned out that the number of characters is much larger than the number of chromosomes. In addition, many traits were inherited together, in pairs, for example, body color and wing length. Morgan made a simple and brilliant conclusion: the reason for the joint inheritance of traits is that genes are located on the same chromosome. Thus, he confirmed the idea expressed earlier by Setton and Boverio that chromosomes are carriers of genes. Genes are linearly located on the chromosome.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.