Genetics deals with the molecular structure and function of genes, gene behavior in context of a cell or organism (e.g. dominance and epigenetics), patterns of inheritance from parent to offspring, and gene distribution, variation and change in populations,such as through Genome-Wide Association Studies. Given that genes are universal to living organisms, genetics can be applied to the study of all living systems, from viruses and bacteria, through plants and domestic animals, to humans (as in medical genetics).
The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of Gregor Mendel in the mid-19th century. Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits via discrete units of inheritance, which are now called genes.
Although genetics plays a large role in the appearance and behavior of organisms, it is the combination of genetics with what an organism experiences that determines the ultimate outcome. For example, while genes play a role in determining an organism's size, the nutrition and health it experiences after inception also have a large effect.
Researchers have identified the gene that ultimately controls the production of tooth enamel, a significant advance that could some day lead to the repair of damaged enamel, a new concept in cavity prevention, and restoration or even the production of replacement teeth.
The gene, called Ctip2, is a "transcription factor" that was already known to have several functions - in immune response, and the development of skin and the nervous system. Scientists can now add tooth development to that list.
"It's not unusual for a gene to have multiple functions, but before this we didn't know what regulated the production of tooth enamel," said Chrissa Kioussi, an assistant professor in the College of Pharmacy at Oregon State University. "This is the first transcription factor ever found to control the formation and maturation of ameloblasts, which are the cells that secrete enamel."
The researchers used a laboratory mouse model in this study in which this gene has been "knocked out" and its protein is missing. Such mice lack basic biological systems and cannot live after birth, but allow scientists to study what is there, and what's missing.
In this case, the mice had rudimentary teeth ready to erupt, but they lacked a proper enamel coating, and never would have been functional.
"Enamel is one of the hardest coatings found in nature, it evolved to give carnivores the tough and long-lasting teeth they needed to survive," Kioussi said.
With an understanding of its genetic underpinning, Kioussi said, it may be possible to use tooth stem cells to stimulate the growth of new enamel. Some groups are already having success growing the inner portions of teeth in laboratory animal experiments, but those teeth have no hard coatings - the scientists lacked the genetic material that makes enamel.
