Concept 2: Genes are stable, passed on in sex cells and control traits
We now know that genes are segments of DNA, the deoxyribonucleic acid molecule that makes up chromosomes. DNA is a stable molecule and therefore genes are stable. They maintain their structural integrity as they are copied and passed on from cell to cell and from generation to generation. Because they maintain their structure, genes can reliably encode genetic information, instruct the cell how to make specific proteins and ultimately control traits or characteristics in the organism. Geneticists use the term phenotype to designate the trait or combination of traits observed in an individual.