The Human Genome Project completed mapping of the genetic sequencing of human DNA in 2005. One discovery the 15-year investigation of genetics turned up is that just about every disease we are aware of has some sort of genetic factor associated with it [source: National Human Genome Research Institute].
Diseases can be the result of a variant gene passed down from parents, a mutation occurring on a gene, or one of these two factors working in conjunction with environmental factors, like smoking or poor eating habits. It's not possible for a physician to examine the external physical characteristics of a patient to determine if he has attention-deficit hyperactivity disorder (ADHD) or insomnia. But factors such as ADHD and trouble sleeping, combined with a study of physical characteristics, can help doctors in diagnosing genetic disorders.
This study of physical characteristics is called dysmorphology. Dysmorphology is based on an established set of average physical traits. By using these touchstones, physicians can determine whether a patient is displaying the physical characteristics associated with a genetic disorder. For example, eye slits are expected to be horizontal. Depending on the horizontal orientation of a patient's eye slits, say downward towards the nose, a doctor can get a good idea of what kind of disorder he is dealing with.
Other measurements that are examined in dysmorphology and were considered in Hammond's composite database include the distance between the eyes, the width of the bridge of the nose, the size of the chin and the length of the forehead.
While Hammond's programs and dysmorphology can help diagnose genetic disorders using facial characteristics, both are useful only after a person has already begun to develop physically. There are only a handful of genetic disorders that can be treated -- usually through drug therapy. Some genetic disorders that display facial characteristics also come with other, internal problems. People with Williams syndrome, for example, usually also have heart conditions. A swift diagnosis through Hammond's program can see to it that these less-obvious conditions be addressed and treated earlier rather than later.
Genetics has also produced another field, genetic counseling, which seeks to prevent genetic disorders. Through genetic counseling, parents who have or carry genetic disorders can determine the likelihood that they will pass on their mutation to their children.
In addition to being dominant, genes can be recessive, meaning defects in their structure that can lead to genetic diseases don't appear in the person carrying them. Once they're passed along, however, some circumstances -- like gender or a mate who submits another copy of the recessive gene -- can cause the gene to become dominant, appearing in the children. In this sense, genetic counseling can be a good idea for all parents. It is recommended most strongly for parents who suffer from a genetic disorder, who have already produced children with a genetic disorder, or spouses in a consanguineous marriage -- a marriage between blood relatives.
While Hammond's database and dysmorphology in general are benign in nature, genetic counseling does have the potential to become a slippery slope. While parents who become knowledgeable about their own genes and their genes' potential for producing healthy offspring can make better-informed decisions about reproducing, pushed to its extreme, genetic counseling approaches eugenics -- the quest to perfect the human race by eliminating undesirable traits.
For lots more information, including related HowStuffWorks articles, visit the next page.