Summary Class notes - Twin Research in Psychology

- Twin Research in Psychology
- van Bergen
- 2020 - 2021
- Vrije Universiteit Amsterdam
- Gezondheid en Leven
380 Flashcards & Notes
1 Students
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Summary - Class notes - Twin Research in Psychology

  • 1603753200 Lecture 1A: Historical perspective & Mendel

  • Which childhood psychopathology is the most heritable?
  • Do genes en environment always play a rol in complex traits?
  • Are environmental influences random?
    No, we choose them.
  • What said hippocrates?
    He believed that humans reproduce trough an egg that swims through the body and picks up gemmules.
  • What said pythagoras?
    A complete mini human was present in every sperm cell. He couldn't explain why some children look like their mothers. (preformationism)
  • What said Aristotle?
    He believed that humans came form menstrual blood. The temperature determined if it would be a girl or boy. Cold: girl and warm: boy.
  • What did Carl linnaeus?
    He created a system that systematically categorize the different species he saw.
  • What said Lamarck?
    He focused on the inheritance of acquired characteristics. The use and disuse of traits creates changes in life, but this will lead to that we will look all the same.
  • What said Galton?
    He realized that there is some inheritance of intelligence/ability. He made a pedigree, where he found out that you look more like your parents than your uncle and aunts. An IQ test can demonstrate genetic relationships between people.
  • Explain Mendel's First law: The law of segregation.
    A recessive element is expressed only if both elements are recessive. While a dominant element is expressed when one or two are present.
  • Definition Punnett Square
    It is used to predict the genotypes of a particular cross or breeding experiment.
  • Explain Mendel's 2nd law: The law of independent assortment:
    The inheritance patterns of one trait will not affect the inheritance pattern of another.
  • Definition genotype
    Combination of alleles at a locus
  • Definition chromosome
    Physical units of inheritance
  • Definition Mendelian disorders
    Disorders that follow the Mendelian inheritance patterns.
  • Definition Huntington's disease
    It's a inherited brain disorder causing very fast worsening of the physical, cognitive and emotional self. The risk of HD is 50% because of a dominant allele.
  • Definition PKU
    PKU is a metabolic disorder caused by a deficiency of the liver enzym phenylalanine hydroxylase (PAH). It's caused by a recessive allele.

    It prevents normal metabolization of phenylalanine (Phe). This is present in protein rich foods, so the disease can be managed by eating protein low. There is a treatment and untreated individuals may give a musty odor and excrete lare amounts of Peh in their urine. PKU individuals have light hair/skin.

    Damage occurs to the central nervous system and leads to mental retardation. 1 in 50 individuals are carriers.
  • Definition carriers
    Offspring with only one copy of the recessive allele.
  • Definition Hardy-Weinberg equilibrium
    The frequencies of alleles and genotypes do not change across generation unless forces such as natural selection or migration change them.
  • For which cases the 2nd Mendel's law applies?
    1. For genes on different chromosomes
    2. For genes that are far apart on the same chromosome.
  • For which cases the 2nd law doesn't apply?
    1. Linkage: genes are close together on the same chromosome which inhibits crossing.
    2. X-linked inheritance

  • When does crossing-over happens?
    During meiosis
  • Definition recombination
    A process that occurs during meiosis in which chromosomes exchange parts
  • Definition linkage analysis
    Identify the location of a gene on a particular chromosome
  • Definition centimorgan (map unit)
    The distance between two loci estimated by the number of recombinations per 100 gametes.
  • Cause color blindness
    Color blindness is caused by a recessive allele on the X chromosome.
  • Definition qualitative traits
    Traits that are influenced by a single gene. These traits follow a simple pattern of inheritance and the phenotypes have distinct categories (present/absent). Traits expression is unaffected by the environment.
  • Examples qualitative traits
    Examples are: HD, PKU and Cystic fibrosis.
  • Definition quantitative traits (polygenic/complex traits)
    Traits are influenced by multiple genes. These genes follow a complex pattern of inheritance. The phenotype is expressed on a continuum and the trait expression may be altered by the environment. These traits are nominal distributed in a bell-shaped curve.
  • Examples of quantitative traits
    Alzheimer and behavioral traits
  • Heritability in order form high to low
    Height, schizophrenia, anxiety disorder, depression
  • Definition morbidity risk estimate/lifetime expectancy.
    The chance of being affected during an entire lifetime
  • Definitie relative risk
    Chance to develop a disorder when a family member has the disorder.
  • Definition concordance/discordance
    The presence/absence of a particular condition in two family members.
  • Definition liability-threshold model
    A model that assumes that dichotomous disorders are due to underlying genetic liabilities that are normally distributed. The disorder appears only when a threshold of liability is exceeded.
  • Symptoms HD
    The disease leads to severe incapacitation and eventual death. It usually affects adults (30-45 years). But symptoms can also appear in children.

    The symptoms are:

    • Uncontrollable movements
    • Abnormal balance when walking
    • Slurred speech    
    • Thinking difficulties
    • Personality changes

    There is no cure or effective treatment
  • Definition liability-threshold model
    A model that assumes that dichotomous disorders are due to underlying genetic liabilities that are normally distributed. The disorder appears only when a threshold of liability is exceeded.
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Definition social media language
Certain words are more mentioned with ADHD comparing to fit people
What can influence the gene expression?
  • Environmental exposures
  • Stresses
  • Diet
  • Lifestyle
How you can use polygenic scores?
Check the size of genetic predisposition to certain diseases
How to measure polygenic scores?
Plot DNA sequences against complex traits
DNA markers can together be used for:
  • Research individual differences without twins and adoptees studies
  • Make individual predictions, instead for all family members
  • Predict risk long before the disorder appears 
Definition development genetic analysis
Considers change as well as continuity during development troughout the human lifespan
Is quantitative genetics about the environment?
Yes it is about the genetics and environment
What indicates abnormal is normal?
Common disorders are the extremes of the normal population
Are environmental effects shared by children growing up in the same family?
How much of the variance in stressful life events can be explained by genetic influence?