Behavioral genetics

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The behavioral genetics is that part of the field of genetics , of the influence of genes on the behavior studied in animals and humans. In this biological research area, developmental genetics , ethology and psychology (especially evolutionary psychology and developmental psychology ) overlap .

Francis Galton

Beginnings

The classical behavioral geneticists examined the heritability (heredity) of behavioral traits.

Heritability is a measure of how much genetics contribute to the expression of a trait. Heritability measures how much of the variance within a given population is due to genetic factors. If the height heritability is approximately 0.69, it means that 69% of the height differences between individuals within a given population are due to genetic factors. The degree of heritability can vary due to the differences that exist between different populations.

Francis Galton published in 1869 the first empirical study of human behavior genetics: " Hereditary Genius " ( Hereditary Genius ). Galton sought evidence that “man 's natural faculties are inherited under exactly the same conditions as the forms and physical properties of the entire organic world. “Today in cognitive neuroscience there is widespread agreement that very few genes are specifically responsible for a certain function or property and that the environment does not solely influence the development of an individual. Galton's research focused on kinship structures through inheritance of aptitude and talent. Galton correctly suspected that the similarity among relatives may be due to both the common genes and the common environment. At present, a distinction is made between four different mechanisms of system-environment interaction through which genetic predisposition and the individual environment influence one another.

  • Under epigenetic mechanisms of the influence of environmental factors is understood to whether and when it comes to gene expression. However, the nucleotide sequence of the individual's DNA does not change due to environmental influences.
  • The development context influences heritability. Maximum heritability can be found in development contexts with high equality of opportunity. Minimal heritability can be found in highly restrictive development contexts, such as those caused by high environmental risks or strong social control of behavior that is tolerated within the population.
  • The facility-environment-correlation (rGE, also: genotype-environment-covariation, facility-environment-covariation) describes the influence of the genotype of an individual on the environments with which it comes into contact. Genotypes are not to be found normally distributed in environments. There are three types of plant-environment correlation that show how individuals are distributed across environments.
    • The passive system-environment correlation refers to the effect of the parental environment, which the individual has not yet chosen himself, but which has a significant impact on his development.
    • The reactive disposition-environment-correlation refers to the uptake of genotype-influenced characteristics (e.g. affinity for music / mathematics) of the individual by other people in his environment. Examples of such people are teachers or classmates.
    • The active system-environment-correlation concerns the independent search for or creation of certain environments by the individual, which in turn influences his development.
  • The plant-environment-interaction (G x E, also: genotype-environment-interaction) describes how the presence of a certain allele in combination with a certain environmental influence reduces or increases the probability of developing a trait.

present

Current behavioral genetics studies certain population groups in anthropological research, twin research, and adoption research . The latter should make it possible to separate “nature” and “nurture” or “plant” and “environment” from one another. That means researching which differences between twins and (adopted) siblings are genetically determined or due to environmental conditions.

In twin studies, an investigation into a trait between monozygous (identical) twins who grew up separately and thus live in different environmental conditions is carried out. Another possibility is a comparison with regard to the examined trait between monozygous (identical) and dizygous (dizygotic) twins who grew up together. If the monozygous twins are more similar in comparison to the dizygotic twins, this indicates a genetic influence or determination of the trait examined.

In adoption studies it should be considered whether the adopted child is more similar to the biological parents ("Nature") or the adoptive parents ("Nurture"). The child shares the genes with the biological parents, but not the environment. The child shares the environment with the adoptive parents, but not the genes. One problem with adoption studies is that the biological parents of the child cannot be found and therefore testing is not possible. An alternative, which is mostly used, is that a comparison is made between the adopted child and the unadopted sibling living in the same household.

The Behavioral Biology focuses its attention on by animal breeding reached breeding lines and results to genetically inherited indistinguishable from environmental influences by Conditional.

The main motive of behavioral research is the search for clues as to how strongly the behavior is genetically influenced. In psychology, this phase lasted mainly in the first half of the 20th century because of the special influence of so-called classical comparative behavioral research . Later behavioral genetic studies (by Seymour Benzer among others ) shifted their area of ​​investigation to quantitative methods . Today, the main focus is on the application of molecular genetic methods and techniques to localize individual genes that influence behavior or specific cognitive aspects (e.g. reading ability).

At present, behavioral genetics is particularly focused on psychiatric genetics , studying psychological phenomena such as schizophrenia , bipolar disorder , Alzheimer's disease and alcoholism . Recently, leading behavioral geneticists published a list of the ten best replicated research in their field. This includes the following statements (original):

  1. All psychological traits show significant and substantial genetic influence
  2. No traits are 100% heritable
  3. Heritability is caused by many genes of small effect
  4. Phenotypic correlations between psychological traits show significant and substantial genetic mediation
  5. The heritability of intelligence increases throughout development
  6. Age-to-age stability is mainly due to genetics
  7. Most measures of the “environment” show significant genetic influence
  8. Most associations between environmental measures and psychological traits are significantly mediated genetically
  9. Most environmental effects are not shared by children growing up in the same family
  10. Abnormal is normal

literature

  • Robert Plomin, John C. DeFries, Gerald E. McClearn, Peter McGuffin: Behavioral Genetics . Palgrave Macmillan, 2008 (5th edition). ISBN 978-1-4292-0577-1 . (German: Peter Borkenau (translator), R. Riemann (translator), FM Spinath (translator): Genes, Environment and Behavior: Introduction to Behavioral Genetics . Huber, Bern (1999). ISBN 3-456-83185-4 )
  • Peter Borkenau: Plant and Environment. An introduction to behavioral genetics . Hogrefe Verlag (January 1, 1993). ISBN 3-8017-0662-1
  • Jamie Ward:. 3. Edition. Taylor & Francis Ltd., 2015, ISBN 978-1-84872-272-9 . Retrieved from https://ebookcentral.proquest.com

Web links

Individual evidence

  1. ↑ Gibran Hemani, Jian Yang, Anna Vinkhuyzen, Joseph E. Powell, Gonneke Willemsen: Inference of the Genetic Architecture Underlying BMI and Height with the Use of 20,240 Sibling Pairs . In: The American Journal of Human Genetics . tape 93 , no. 5 , November 2013, p. 865-875 , doi : 10.1016 / j.ajhg.2013.10.005 , PMID 24183453 , PMC 3965855 (free full text) - ( elsevier.com [accessed June 29, 2020]).
  2. ^ A b c d Jamie Ward: The Student's Guide to Cognitive Neuroscience . 3. Edition. Taylor & Francis Ltd, 2015, ISBN 978-1-84872-271-2 .
  3. ↑ a b c d e Michael Rutter, Terrie E. Moffitt, Avshalom Caspi: Gene-environment interplay and psychopathology: multiple varieties but real effects . In: Journal of Child Psychology and Psychiatry . tape 47 , no. 3-4 , March 2006, ISSN  0021-9630 , p. 226–261 , doi : 10.1111 / j.1469-7610.2005.01557.x ( wiley.com [accessed June 29, 2020]).
  4. ^ Genotype-environment correlation. Retrieved June 29, 2020 .
  5. ↑ Behavioral Genetics . Retrieved June 29, 2020 .
  6. ^ Genotype-environment correlation. Retrieved June 29, 2020 .
  7. ^ Genotype-environment correlation. Retrieved June 29, 2020 .
  8. ^ Genotype-environment correlation. Retrieved June 29, 2020 .
  9. ^ Genotype-environment interaction. Retrieved June 29, 2020 .
  10. ^ Robert Plomin, John C. DeFries, Valerie S. Knopik, Jenae M. Neiderhiser: Top 10 Replicated Findings From Behavioral Genetics . In: Perspectives on Psychological Science . tape 11 , no. 1 , January 27, 2016, p. 3–23 , doi : 10.1177 / 1745691615617439 ( sagepub.com - full text freely accessible).