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Genetics

Genetics is the study of genes and the variation of characteristics that are influenced by genes—including physical and psychological characteristics. All human traits, from one's height to one's fear of heights, are driven by a complex interplay between the expression of inherited genes and feedback from the environment.

Scientists are tasked with a massive but increasingly plausible mission: mapping the pathway from one's genes to the person one sees in the mirror. What they learn about the power of genes has implications for understanding mental illness and psychological differences between individuals, as well as the psychological effects of non-genetic factors.

Why Genes Matter in Psychology

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Genes help to define who an individual is inside and out. While non-genetic factors have a role to play, too, what scientists have learned about these influences can clash with common wisdom. A characteristic or behavior that appears to result from a child’s upbringing—such as a proneness to mental illness or divorcemay actually be largely a product of the genes she inherited from her parents. In fact, research investigating the influence of the family environment suggests that it accounts for a surprisingly small amount of the difference between people on characteristics that scientists measure.

What is a gene?

A gene is the basic unit through which genetic information is stored and passed between generations. Physically, a gene is a specific section of one of the long, double-helix-shaped DNA molecules that appear in each cell of the body. Genes vary in size, comprising anywhere from hundreds to millions of the nucleotides that collectively make up DNA. Many (but not all) genes provide chemical “instructions” for the creation of protein molecules, or serve other roles that are integral to the function of an organism. Different versions of the same gene are called alleles.

What is the genome?

The genome is the entirety of the genetic material contained in an individual. Human DNA is estimated to contain between 20,000 and 25,000 genes. The vast majority of each person’s genome is identical to that of the next person, but the portion that differs is consequential for how individuals develop.

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The Science of Genetics and Behavior

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It may seem obvious that the genes people inherit from their parents and share with their siblings have an effect on behavior and temperament. Individuals are often noticeably more similar in a variety of ways to immediate family members than they are to more distant ones, or to non-relatives. Of course, there are plenty of notable differences within families as well. Scientists have employed an array of methods to drill down into how and to what extent genetic differences truly account for psychological differences.

What is behavioral genetics?

Behavioral genetics, or behavior genetics, is the study of psychological differences between individuals and how genetic and non-genetic factors create those differences. Among other questions, behavioral genetics researchers have sought to determine the extent to which various specific differences in people’s behaviors and traits can be explained by differences in their genetic code.

How do we know genes matter for behavior?

Scientists use specialized methods to explore the links between genes and individual differences. Studies of twins who either do or do not have identical genomes allow for estimates of the degree to which genes drive the variation in psychological traits. Other methods, such as studying adopted children and their adoptive and biological parents, have been used as well. In recent years, genome-wide association studies (GWAS) have emerged as a major approach in behavioral genetics. A GWAS uses genetic testing to identify numerous genetic differences across many individuals, then analyze the association between these differences and personality traits or other outcomes.

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