The words "genetics" and "genomics" are often used interchangeably. Human beings have somewhere between 25,000 and 30,000 genes that code for different processes in the body. Strung together, those genes, along with non-coding regions in between (which scientists are still trying to decipher), collectively make up the human genome.
The science of human genetics focuses on individual genes in the human genome, to determine which genes are related to disease, or determine certain physical traits. Genomics, on the other hand, is a term used when scientists look at several genes simultaneously or when they study how different genes work together.
Everyone's genome is unique and, through genetic testing, physicians may learn whether you are at risk for certain illnesses or predict how you will respond to some medications. For this reason, genomics is a key part of personalized medicine.
The Building Blocks of Life
Deoxyribonucleic acid, or DNA, contains the genetic instructions for the development and functioning of all living things. You can think of your DNA as your body's blueprint or instruction manual. DNA stores information in a sort of code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). A always pairs with T, and C always pairs with G, so we refer to them as "base pairs."
It is the order of these pairs that determines the nature of the information encoded in our DNA--everything from eye color to an elevated risk for certain cancers. The base pairs are arranged in a spiral-like ladder called a double helix. Human DNA consists of about three billion base pairs, more than 99 percent of which are the same in all people! It's the remaining one percent that accounts for the differences between any two individuals.
Your DNA is found inside the nucleus of each of your cells, condensed into 23 pairs of chromosomes. Each chromosome carries multiple genes. A gene is a specific area on a chromosome that carries the code for a specific function or trait. Individual genes can be anywhere from 1,000 to 100,000 base pairs long.
Genetic tests examine DNA samples taken from a person's blood, saliva, or tissues. Genetic testing can look for mutations, or changes in DNA. Testing can also reveal missing or extra copies of a gene, genes that are too active, or genes that are turned off. Some of the uses of genetic testing include:
- Confirming a diagnosis based on a person's symptoms and/or appearance.
- Finding out whether a person is a carrier for a genetic disease.
- Prenatal testing so that expectant parents can know whether a developing baby will have a genetic condition.
- Newborn screening to determine whether an infant has abnormal or missing proteins that can cause disease.
- Determining whether a person has an inherited risk for a certain disease before symptoms start.
- Pharmacogenetic testing to determine the type or dose of a medicine that is best for a certain person.
It's only natural for people whose families have a genetic disease in their history to worry about their future and the prospect of their children inheriting the family condition. Testing can take away some of that uncertainty. Learning that a disease-causing mutation is not in your genes is a relief. And finding out that your genes do carry a disease-causing mutation can still provide benefits. In some cases, you can take steps to lower your chance of developing a disease through frequent screenings, medications, and healthy lifestyle changes.