Summary Genes & Environment Interplay/Interplay genes and environment, VU
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Course
Samenspel van Genen en Omgeving (P_BSAGEOM)
Institution
Vrije Universiteit Amsterdam (VU)
Summary of all lecture notes from “Genes and Environment Interplay” /"Interplay between genes and environment”. In addition, most chapters of Behavioral Genetics by Knopik et al are also summarized. (version used in 2018).
INDEX
1. Introduction to Behavioral and Molecular Genetics 2
® Historical Perspective & Mendel’s Laws 2
® Biological Basis of Heredity 5
® Animal Models 6
2. Nature and Nurture 8
® Estimating genetic and environmental influences 10
® The interplay between genes and environment 11
3. From Genes to Behavior 13
® Identifying genes 13
® Substance use (disorders) 16
4. Cognition and Child Development 19
® Cognitive (dis)ability 19
® Developmental psychopathology 24
5. Adult Personality and Psychopathology 27
® Personality(disorders) 27
® Psychopathology 30
6. Health Psychology 33
® Health & aging 33
® Pathways between genes and behavior 36
7. Interplay of Genes and Environment: The Future 39
This summary includes (almost) everything from the lectures & the book. Lecture 13 (The Future) was not
included; that part of the summary only contains the chapter from the book (pg. 39 & 40)
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This summary is made by a student!
Studying from it and relying on it for 100% is your own responsibility.
THANKS & GOOD LUCK!!! J
J YOU CAN DO IT !!!!
, 2
Introduction to Behavioral and Molecular Genetics (Knopik, ch. 1, 2, 3, 4)
- Nature vs nurture debate à always both but different balance
o Some things are 100% genetic, e.g. Down Syndrome or fragile X syndrome, but does NOT
mean that their life is determined by their genes. The environment can stimulate or inhibit
their potentials
HISTORICAL PERSPECTIVE & MENDEL’S LAWS
- Hippocrates
o Looked at transmission in families
o Males “make” the embryo, females are just an incubator
- Pythagoras
o Performationism - organisms develop from miniature versions of themselves
o “pieces” are collected from throughout a man and incubated in the female
- Aristotle
o Not just the male makes the embryo! Then how can you birth a daughter?
o There are male parts, but the females menstrual blood “builds” the baby
§ Diet & temperature determine sex of the baby
- Carl Linnaeus
o First to investigate animal kingdom & plants à also transmission
- Jean Baptiste de Lamarck
o Example = giraffes adapt to their
environment
o Lamarckism – adaptation can be
crystallized (incorrect view of evolution)
- Charles Darwin
o Suggested plant and animal species appear
capable of improvement (finches)
o Theory of evolution
§ Variation within population is
(partly) due to heredity)
§ Possibly some traits affect chance
of survival
§ Passed on à cumulation of changes à “new” species à different habitats
(can also be the other way around, different habitats à different species) = natural
selection
o Shows that
1. It’s difficult to know the mechanisms driving evolution
2. Behavior is often the “cutting edge” of natural selection
o Survival of the fittest – the one that fits the environment best will survive
§ BUT they also have to reproduce!!! Otherwise no point in being the best
o Darwin’s theory holds best, but some gaps remained concerning the actual mechanism
- Galton
o Looked at transmission of “eliteness”, i.e. always the same families had power & were most
intelligent. The closer the family relatedness, the higher the incidence of high GMA
o Concluded nature >>> nurture!
- Pre-Mendelian Concepts of Heredity and Variation
o Heredity
§ J.L. Lush: like produces like, but like does not always produce like
§ In Darwin’s time: provisional hypothesis of pangenesis – mini replicas of parent cells
are thrown off by each cell throughout its development (wrong)
, 3
o Variation
§ How is variability induced/maintained?
• Darwin: environmental factors alter the stuff of heredity
Mendels’ laws and beyond
- Researched peas.
o Crossed green and yellow à F1 all yellow
o But then green came back in the F2, HOW?
- Law of segregation (Mendel’s 1st law) – there are two “elements” of
heredity for each trait. One of these can dominate the other. A recessive
(nondominant) element is expressed only if both elements are recessive
o This idea was picked up again 30 years later, now called alleles &
genes
- Law of independent assortment (Mendel’s 2nd law) – the inheritance of
one trait is not affected by the inheritance of another trait
o So the fact that a white cat has a short tail and a brown cat a long tail, does not mean that if
you would cross them, there could only be white short-tailed cats and brown long-tailed
cats. It’s also possible there will be white long-tailed cats and brown short-tailed cats.
o This law is actually violated sometimes
§ Genes are carried on chromosomes (threadlike structure that contains DNA and
resides in the nucleus of the cell) and located at a locus. The law is violated when
genes for traits are close together on the same chromosome (linkage). It is
important that they are very close together!!!
- Punnett squares
o A way to determine the chance of getting a specific combination of alleles
o Example using peas
§ You can see here we have crossed green peas (top - yy) with yellow peas (bottom -
Yy).
§ The combination of the different possible alleles show that 50% of
the peas will be yellow and 50% of the will be green
§ YY = homozygote dominant
§ Yy = heterozygote
§ yy = homozygote recessive
Important terminology
- Gene – basic unit of inheritance
- Allele – alternative variants of gene
- Genotype – combination of alleles at a locus
- Phenotype – observed trait of an organism
- Homozygosity – 2 the same alleles at a locus
- Heterozygosity – 2 different alleles at a locus
- Chromosome – physical units of inheritance
- Genome – all DNA sequences of an organism
- Locus – site of a gene on a chromosome
- Autosome – all other chromosomes than X or Y
2 examples
, 4
Huntington’s disease (HD)
- Caused by a dominant allele (often have Hh, HH is very rare)
- Offspring will also inherit normal allele (h) form unaffected
parent (the right one in this case)
o So there is a 50% chance of having offspring with HD
- Why does this persist in the population?
o Likely because the disease does not become lethal until
after reproductive years
o Nowadays, using DNA markers, we can determine for certain whether a person has the HD
gene
Phenylketonuria (PKU)
- Caused by two recessive alleles (pp)
- People with only 1 p (Pp) are called carriers – they are not
afflicted with the disorder
- If the parents are both carriers of PKU, there is 25% chance
that their offspring will have PKU, 50% chance they will be
carriers and a 25% chance they will be unaffected
HD & PKU are both single-gene disorders, however they are often
not that simple. Many different mutations of the gene occur, and they all have different effects
Beyond Mendel
- Multiple gene inheritance
o HD & PKU: a single gene is necessary and sufficient
§ Necessary – you will have HD only if you have the H allele
§ Sufficient – if you have the H allele, you will have HD
o Diseases such as schizophrenia are more complex – they are polygenetic traits – influenced
by multiple genes. Each of these genes is inherited according to Mendel’s law.
- Quantitative genetics – the notion that multiple gene effects lead to quantitative traits
o Fisher & Wright
o Accounts for the resemblance of relatives, and this should
increase with increasing degree of genetic relatedness – how
close you genetically are to someone
§ Relatives are always listed around an individual in the
center (index case/proband)
o 2 most important experimental designs for behavioral genetics
are twin studies and adoption studies.
o But if e.g. schizophrenia is caused by multiple genes, how is it a
dichotomous outcome (i.e. you are schizophrenic or not)? à
liability-threshold model – assumes that dichotomous disorders are due to
genetic liabilities that are distributed normally. The disorders appears only
when a threshold of liability is exceeded.
- The X-chromosome – some traits occur more often in males than in females
o 23rd chromosome pair = sex chromosomes (M: XY, F: XX)
o E.g. color blindness = linked to recessive gene only on X chromosome. Men color blind: only
need on “c” allele on X. women: need two c on both X’s à Much less likely!!
o This also allows for normal daughters of a colorblind father, to have a colorblind son.
o More extensive scenarios are explained in the book on pg. 39 – 40.
o Detecting X-linkage is much easier than locating genes on other chromosomes.
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