Gene s are located within particular segments of the DNA molecule. The genes govern nearly all the physical traits of the organism from pigmentation to anatomy. Genes almost always come in pairs, one inherited from the mother and one from father. The genes are contained within the chromosomes . To use an analogy, if the genes are the pages of a book, then the chromosomes are the chapters, and the complete chromosome set is the book.
Genes can be either dominant or recessive .
For example, in humans, the gene for brown eyes is dominant and the gene for blue eyes is recessive. If a child receives a blue eye gene from the father and a brown eye gene from the mother, the child will have brown eyes. In order for the child to have blue eyes, they must receive a blue eye gene from both parents. A process by which the DNA structure is altered, sometimes by radiation. To use a crude analogy, the radiation is like a bowling ball that strikes the DNA molecule and mixes it up.