Lesson 3: DNA's Role in Determining Your Traits
Because most traits are influenced by several genes and environmental factors, it is not possible to predict all the traits that will develop in an individual, even when the person's genotype is known. In addition, the low penetrance of many alleles means that only a low percentage of people with any particular allele will have the associated trait.
The term genetic potential is used to
describe the information in a person's genome
(their genotype) that could produce particular
traits if environmental factors were favorable
for the development of those traits.
For example, if a person has the DR4
allele, they have the genetic potential to
develop rheumatoid arthritis, but other factors
in addition to that allele must come into play
before the disease will occur.
Most of us have the genetic potential to
produce strong muscles and a lean body, but
those traits typically do not appear unless a
fitness program and diet regime are followed.
Another common way of describing the influence of alleles on traits is to determine the risk that a particular allele has on development of a particular disease. For example, about 2% of adults over age 50 have rheumatoid arthritis. About 20% of people over age 50 with the DR4 allele have rheumatoid arthritis. Although most people with DR4 do not get rheumatoid arthritis, if you have DR4, you are much more likely to get the disease than if you do not have DR4.
