Scientists have studied the genetic makeup of life forms on the planet since the 1800s, and advances in technology over the years have helped to continue this research into the basic building blocks of life. The discovery of the helical structure of DNA in the 1950s was an important leap forward that created the field of molecular genetics and a greater understanding of how genes function. From 1990 to 2003, researchers compiled data on human genomes to help broaden our understanding of what genes do and how they regulate the human condition. This effort permitted a number of new discoveries about human genes and a host of new research to learn more about the differences and similarities in the human population.
What Are Genes?
Genes are subunits of DNA, deoxyribonucleic acid, the database of instructions that make up every living creature. Genes provide the recipe for the individual’s makeup, for such features as eye color, hair color, body shape, abilities and lifespan. As scientists compile data for the human genome project, they are coming to understand new information about how genetic data is transmitted from generation to generation. Some of this information is providing new avenues of investigation for medical treatment and understanding of the history of human populations.
The Number of Human Genes
In the past, scientists postulated that there must be a very large number of genes, as much as 3 billion genes, because human beings are so diverse and have so many different characteristics. However, the Human Genome Project discovered that human beings possess only 20,000 to 25,000 genes. The rest of the DNA was at first thought to filler material that didn’t contribute to the manufacture of proteins that are essential to life. But they soon learned that this “junk DNA” performed special functions in controlling genes. Geneticists now know these “epigenetic markers” play an important role in which genes are turned on and off, highlighting special features on an as-needed basis.
Although the diseases that run in families that are carried in the genes have been known for some time, research on genetics has found that it is rarely just one gene that causes a disease to occur in an individual. Generally, a number of genes must be in play to trigger the physical expression of the disease. In some cases, only some of the contributing genes are carried by individuals in their DNA. Mating with someone who has the other genetic components may then produce an individual who is affected by the disease. In addition, environmental factors have an influence on whether some genes become active or not. This new information complicates our understanding of how genetic diseases occur. Someone with a particular genetic history may not necessarily get the disease or may not necessarily produce a child who is susceptible to the disease
More Then One Copy of Some Genes
Scientists have also learned that humans have additional copies of genes that can evolve in different directions from each other. This “copy number variation” allows new traits to develop that can provide additional survival advantages and can be responsible for the evolution of a species into a new direction.
Changes in Regulatory Sequences Can Lead to Gene Changes
The small changes in non-gene components of the DNA can be the directing forces of genetic change. These components involve small chemical changes that take their cue from the environment around them, creating more favorable internal structures for survival and forcing changes in the genes themselves. Genes are not just permanent instructions for a particular species. They are also malleable structures that conform to external needs, changing and evolving as the environment dictates.
Research on genes continues in laboratories around the world, increasing our understanding of the subtle interplay of genetic forces and how they help us survive. A number of ethical considerations have come into play regarding the future of gene manipulation and the creation of “designer babies” with superior traits. These issues, as well as other considerations, will be a part of our public debate about the science of genetics for decades to come.