Gene & Environment Interaction
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)
CLAIMER
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.
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)
CLAIMER
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.
