Genetic mapping is being used to determine the location and function of specific genes on specific chromosomes. These genetic maps have been used to identify genes responsible for various disorders, such as Huntington's disease, a progressive disorder characterized by muscle deterioration, personality change, and intellectual decline in adults who carry the gene. The Human Genome Project is a massive collaborative effort to map out human genes and address ethical, social, and scientific issues related to human genetics. Mapping out human genes is an enormous undertaking. Deteriming what influences these genes have is even more enormous, particularly since much of human behavior appears to be polygenetic, that is, influenced by more than one gene.
Intelligence is one form of human behavior that is polygenetic.
Psychologists are still defining and refining the concept of intelligence and how to measure intelligence. Their collaborative efforts have yielded a gene that makes a very small but potentially important contribution to intelligence. For Students Article Summary Family, twin, and adoption studies indicate that genes have some influence on intelligence. Identifying the genetic influence is a monumental task, however. Intelligence is also strongly influenced by the environment and the interaction between genes and the environment, making it difficult to isolate the independent effect of genes on intelligence.