How Genetic Differs From Heredity

In the simplest terms, the adjective “genetic” means anything that pertains to a person’s gene sequence that exists within every living cell. Genes are the basic component of heredity in humans and other living organisms.

Genes

Genes are made up of DNA, or deoxyribonucleic acid. According to the National Human Genome Research Institute, we have an estimated 20,000 genes. Many of our genes contain the instructions for building a protein, but the majority of our DNA is "non-coding", meaning that it does not produce a protein.

Remarkably, approximately 99% of genes are the same in all people, with the remaining tiny proportion responsible for the differences we see in height, skin color, weight, and other physical traits. Some mutations—changes to a gene's DNA sequence—cause disease while others have no effect at all.

The Genetic Theory of Aging

The genetic theory of aging suggests that longevity is also determined by our genes, and some research — such as studies involving identical twins — supports this hypothesis. Other studies have estimated that a person’s lifespan is only about 25% attributable to their heredity and much more likely to be influenced by lifestyle factors like diet and exercise, and harmful habits like smoking or alcohol abuse.

Further, a growing field of health science research called epigenetics aims to determine how gene function can be altered without changes to the gene's DNA sequence.

This area of study looks at influencing factors such as maternal stress or environmental exposure, and can at least partially explain why identical twins have physical differences despite possessing the same genetic makeup.​

Genetic vs. Hereditary

While the term genetic is often used interchangeably with the adjective hereditary, these words don't necessarily mean the same thing. For example, cancer is a genetic disease in that it involves the genes within a cell (causing that cell to divide uncontrollably), but cancer itself may be caused by sun or tobacco exposure and is not necessarily inherited from your parents.