Week 3 Readings

Question 1

What are the three related problems at the intersection of philosophy and science fundamental to our understanding of our relationship to the natural world?

Answer 1

the mind–body problem, the free will problem, and the nature–nurture problem

Question 2

What is behavioral genetics? What is the easiest opportunity we have to observe this?

Answer 2

The science of how genes and environments work together to influence behavior is called behavioral genetics

Adoption study is the easiest opportunity we have to observe this (A behavior genetic research method that involves comparison of adopted children to their adoptive and biological parents)

Question 3

What is quantitative genetics and what methods are examples of it?

Answer 3

Quantitative genetics is the scientific discipline that analyzes similarities among individuals based on biological relatedness. Examples of methods include twin and adoption studies.

Question 4

What does a heritability coefficient measure in quantitative genetics, and why can it be difficult to interpret?

Answer 4

A heritability coefficient measures how strongly differences among individuals are related to differences in their genes, ranging from 0 to 1.

It can be difficult to interpret because, despite being simple to compute, it provides a single measure of genetics’ influence on a trait, which can be misleading and lead to intense debates about the heritability of traits like intelligence, personality, or depression.

Question 5

How do difficulties with nature–nurture problems relate to the mind-body problem and free will?

Answer 5

Difficulties with nature–nurture problems reflect similar complexities found in the mind-body problem and free will. Just as consciousness and choice are not simple or confined to specific brain areas or behaviors, nature and nurture issues also become more complex the more we examine them, challenging the idea of finding straightforward answers or single measures.

Question 6

Which of the following is a process in which the DNA itself is modified by environmental events and those genetic changes are then transmitted to children?

dizygotic mutation.
ecological spreading.
genetic neuroscience.
behavioral genetics.
epigenetics.

Answer 6

epigenetics

Question 7

Adoption study

Answer 7

A behavior genetic research method that involves comparison of adopted children to their adoptive and biological parents.

Question 8

Behavioral genetics

Answer 8

The empirical science of how genes and environments combine to generate behavior.

Question 9

Heritability coefficient

Answer 9

An easily misinterpreted statistical construct that purports to measure the role of genetics in the explanation of differences among individuals.

Question 10

Quantitative genetics

Answer 10

Scientific and mathematical methods for inferring genetic and environmental processes based on the degree of genetic and environmental similarity among organisms.

Question 11

Twin studies

Answer 11

A behavior genetic research method that involves comparison of the similarity of identical (monozygotic; MZ) and fraternal (dizygotic; DZ) twins.

Question 12

What happens in the brain during the critical period of development, and how does it relate to phenotypic plasticity?

Answer 12

During the critical period of brain development, more than 700 neural connections are created each second, with complex gene-environment interactions (G×E) increasing potential contacts between neurons.

Many weak connections are formed and later remodeled, leaving only stable ones.

These changes, known as plasticity, contribute to mature neural networks.

Phenotypic plasticity arises when a single genome produces different outcomes in response to environmental changes, helping organisms adapt to variations and solve future problems.

Question 13

What have studies shown about the role of DNA sequence variation in the inheritance of personality traits and mental disorders?

Answer 13

Studies have shown that common DNA sequence variations and rare mutations account for only a small fraction (1%–2%) of the total risk for inheriting personality traits and mental disorders. The unaccounted heritability suggests that additional molecular and cellular mechanisms are involved.

Question 14

What is epigenetics?

Answer 14

The study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence.

Epigenetic marks include covalent DNA modifications and posttranslational histone modifications.

Question 15

Identical twins share a common __________. They originated from the same __________.

Answer 15

genotype, zygote

Question 16

Why is the study of identical twins particularly useful in epigenetic research?

Answer 16

The study of identical twins is useful in epigenetic research because it eliminates DNA sequence, age, and sex differences, allowing researchers to focus on epigenetic factors when twins are discordant for a disease.

Question 17

What are the enzymes that perform DNA methylation?

Answer 17

DNA methyltransferases (DNMTs)

Question 18

How does DNA methylation affect gene expression, and what is its significance?

Answer 18

DNA methylation, especially in gene regulatory regions like promoters and enhancers, typically leads to gene silencing and reduced gene expression. This process is crucial as it ensures that genes are expressed only when needed, acting as a powerful regulatory mechanism.

Question 19

How do histone modifications, particularly acetylation, influence gene expression?

Answer 19

Histone acetylation, mediated by histone acetyltransferases (HATs), is associated with gene activation and increased expression by promoting DNA demethylation.

Conversely, histone deacetylation by histone deacetylases (HDACs) is linked to DNA methylation, gene silencing, and decreased expression.

These patterns of histone modifications suggest a “histone code” that regulates cell-specific gene expression. Recent research indicates that histone modifications and DNA methylation can mediate the long-term effects of early life experiences on behavior.

Question 20

Define histone modifications

Answer 20

Posttranslational modifications of the N-terminal “tails” of histone proteins that serve as a major mode of epigenetic regulation. These modifications include acetylation, phosphorylation, methylation, sumoylation, ubiquitination, and ADP-ribosylation.

Question 21

Define histone acetyltransferases (HATs) and histone deacetylases

Answer 21

HATs are enzymes that transfer acetyl groups to specific positions on histone tails, promoting an “open” chromatin state and transcriptional activation. HDACs remove these acetyl groups, resulting in a “closed” chromatin state and transcriptional repression.

Question 22

How does early childhood experience influence the development of an individual’s stress response and behavior?

Answer 22

Early childhood experiences, such as the closeness of the parent-infant bond and parental investment, program the development of individual differences in stress responses in the brain. This adaptation influences memory, attention, and emotion, allowing offspring to adjust gene expression for neural circuit organization. This process supports biological defense systems, reproductive success, and adequate parenting for future generations.

Question 23

How does maternal care in early life affect stress responses and gene expression in rats?

Answer 23

Maternal care, such as licking and grooming during the first week of life, programs long-term differences in stress responsiveness in rat pups.
- High maternal care leads to increased expression of the glucocorticoid receptor in the hippocampus and a lower stress response.
- Low maternal care results in decreased histone acetylation, increased DNA methylation of the glucocorticoid receptor gene promoter, reduced gene expression, and a higher lifelong stress response.

Treatments affecting histone acetylation and DNA methylation can reverse these effects, suggesting potential molecular targets for addressing the impacts of childhood maltreatment.

Question 24

How can nutrients influence the epigenome, and what are the potential long-term effects?

Answer 24

Nutrients can influence the epigenome by directly inhibiting enzymes involved in DNA methylation or histone modifications or by altering the availability of substrates required for these processes.

For instance, a diet low in methyl donors during pregnancy can lead to decreased DNA methylation and increased histone acetylation in offspring, affecting gene expression. This suggests that early life nutrition can impact epigenetic programming, potentially influencing health throughout life and serving as a tool for preventing developmental diseases and delaying aging-related processes.

Question 25

What role does DNA methylation play in the hippocampus concerning learning and memory?

Answer 25

DNA methylation in the hippocampus is associated with neuronal activity, and disruptions to genes involved in DNA methylation can lead to learning and memory impairments. It is crucial for maintaining long-term memories, as inhibiting DNA methylation impairs memory.

These findings highlight the importance of DNA methylation in synaptic plasticity and cognitive functions, both of which can be disturbed in psychological illnesses.

Question 26

How do changes in histone modifications influence long-term memory formation?

Answer 26

Changes in histone modifications affect long-term memory formation by altering chromatin accessibility and gene expression.

Increases in histone acetylation and changes in histone methylation promote gene expression, enhancing synaptic transmission and memory formation.

Conversely, increased histone deacetylase activity leads to gene silencing, reduced synaptic plasticity, and impaired memory. Inhibiting histone deacetylases can augment memory formation, highlighting the regulatory role of histone (de)acetylation in memory processes.

Question 27

How do genetic defects in DNA methylation and chromatin machinery affect cognitive function and mental health in humans?

Answer 27

Genetic defects in genes responsible for DNA methylation and chromatin machinery can significantly impair cognitive function and mental health.

Examples include Rett syndrome and Rubinstein-Taybi syndrome (RTS), which are intellectual disability disorders caused by mutations in the MECP2 and CBP genes. Both of these genes are highly expressed in neurons and play a crucial role in regulating neural gene expression.

Question 28

What roles does the MECP2 gene play in cells, and how do mutations in MECP2 affect individuals with Rett syndrome?

Answer 28

The MECP2 gene is crucial for reading DNA sequence, checking DNA methylation, binding to methylated regions to regulate protein presence, and ensuring proper DNA packaging and protein production. MECP2 also influences gene expression related to dendritic and synaptic development and hippocampus-dependent memory.

Mutations in MECP2, as seen in Rett syndrome, lead to genome-wide increases in histone acetylation, neuron cell death, increased anxiety, cognitive deficits, and social withdrawal. This supports the idea that MECP2 and DNA methylation are key epigenetic mechanisms for regulating histone modification and gene expression, which can be disrupted in Rett syndrome.

Question 29

What role does the CBP gene play in cells, and how do mutations in CBP affect individuals with Rubinstein-Taybi syndrome (RTS)?

Answer 29

The CBP gene promotes histone acetylation by binding to specific histones, thereby enhancing gene expression.

In individuals with Rubinstein-Taybi syndrome (RTS), mutations in CBP lead to decreased histone acetylation and cognitive dysfunction. These learning and memory deficits are attributed to disrupted neural plasticity.

In mice with CBP mutations, similar cognitive impairments and reduced histone acetylation are observed.

Additionally, CBP acts as an epigenetic switch to promote the birth of new neurons, and this mechanism is disrupted in the fetal brains of mutant mice, leading to early behavioral deficits. This highlights how environmental cues and histone-modifying enzymes can influence neurogenesis and neurobehavioral development.

Question 30

How are epigenetic changes linked to depression-related behavior and the effects of antidepressant medications?

Answer 30

Epigenetic events that alter chromatin structure have been associated with depression-related behaviors and the effects of antidepressants.

In mice, social avoidance leads to decreased expression of hippocampal genes that mediate depressive responses, and chronic social defeat stress reduces the expression of genes involved in emotion processing.

Similarly, human post-mortem brain samples from individuals with a history of depression show decreased levels of histone markers associated with increased gene expression, indicating that epigenetic regulation plays a role in depression.

Question 31

How do antidepressants and HDAC inhibitors affect gene expression related to depression?

Answer 31

Antidepressants increase histone markers associated with gene expression and can reverse the gene repression caused by stress. This supports the use of HDAC inhibitors as potential treatments for depression. Several HDAC inhibitors have been found to exert antidepressant effects by modifying various cellular targets, thereby promoting gene expression linked to improved mood and emotional regulation.

Question 32

How does the dynamic nature of the epigenome affect the study of psychological disorders?

Answer 32

The epigenome is not static; it can be shaped by developmental signals, environmental influences, and disease states. This dynamic nature presents an experimental challenge in identifying epigenetic risk factors for psychological disorders, as the epigenome can change in response to various internal and external factors over time.

Question 33

Which is the engine of evolution by natural selection:

a) reproductive success
b) survival success

Answer 33

a)

Question 34

What is the sexual selection theory by Charles Darwin?

Answer 34

The evolution of characteristics because of the mating advantage they give organisms.

Question 35

What is intrasexual competition, and how does it relate to sexual selection?

Answer 35

Intrasexual competition is a process of sexual selection where members of one sex compete with each other for the opportunity to mate with a member of the opposite sex.

These successful traits are then passed on more frequently to future generations due to their association with greater mating success.

Question 36

What is intersexual selection, and how does it influence the traits passed on to future generations?

Answer 36

Intersexual selection, also known as preferential mate choice, occurs when members of one sex are attracted to specific qualities in mates, such as bright plumage, signs of health, or intelligence. These desired traits are passed on more frequently because individuals possessing them mate more often. An example is the colorful plumage of peacocks, which evolved because peahens prefer males with brilliant feathers.

Question 37

What are the two basic ways genes can increase their own replicative success?

Answer 37

Genes can increase their replicative success in two ways:

(1) by enhancing the organism’s chances of survival and reproduction (individual reproductive success or fitness), and

(2) by influencing the organism to help genetic relatives survive and reproduce, a concept known as inclusive fitness. This way, genes indirectly promote their own replication by supporting the survival of others who share the same genetic material.

Question 38

What are psychological adaptations?

Answer 38

Mechanisms of the mind that evolved to solve specific problems of survival or reproduction; conceptualized as information processing devices.

a psychological adaptation is a development or change of a mechanism in the mind. For example, take sexual jealousy. First, there is an “input,” such as a romantic partner flirting with a rival. Second, there is a “procedure,” in which the person evaluates the threat the rival poses to the romantic relationship. Third, there is a behavioral output, which might range from vigilance (e.g., snooping through a partner’s email) to violence (e.g., threatening the rival).

Question 39

What are physiological adaptations? Provide one example.

Answer 39

Adaptations that occur in the body as a consequence of one’s environment.
One example of a physiological adaptation is how our skin makes calluses. First, there is an “input,” such as repeated friction to the skin on the bottom of our feet from walking. Second, there is a “procedure,” in which the skin grows new skin cells at the afflicted area. Third, an actual callus forms as an “output” to protect the underlying tissue—the final outcome of the physiological adaptation (i.e., tougher skin to protect repeatedly scraped areas).

Question 40

What does sexual strategies theory propose?

Answer 40

Sexual strategies theory proposes that humans have evolved a variety of mating strategies, both short-term and long-term.

These strategies can vary depending on factors such as culture, social context, parental influence, and an individual’s mate value (desirability in the “mating market”).

Question 41

What is Error Management Theory (EMT) and how does it apply to decision-making in uncertain situations?

Answer 41

Answer: Error Management Theory (EMT) deals with the evolution of human thinking, decision-making, and evaluation of uncertain situations. It suggests that when faced with uncertainty, the costs of potential errors influence our decisions.

For example, if you hear a rustle in the woods that could be a snake or just the wind, avoiding the potential threat (a minimal cost) is safer than ignoring it and risking danger (a high cost). Thus, EMT explains why we often err on the side of caution in uncertain situations.

Question 42

What are “cost asymmetries” in the context of Error Management Theory (EMT), and how do they shape decision-making?

Answer 42

“Cost asymmetries” refer to situations where one option has a low cost but a high reward (e.g., avoiding a potential threat) and the other has a low reward but a high cost (e.g., ignoring a threat and facing danger).

According to EMT, repeated encounters with such decisions throughout evolutionary history have led to an adaptive bias: humans psychologically adapt to prefer the choice that minimizes the potential cost of errors, usually erring on the side of caution.

Question 43

Another example of EMT is the auditory looming bias: Have you ever noticed how an ambulance seems closer when it’s coming toward you, but suddenly seems far away once it’s immediately passed? With the auditory looming bias, people overestimate how close objects are when the sound is moving toward them compared to when it is moving away from them.

Answer 43

The auditory looming bias is the tendency to overestimate how close objects are when their sound is moving toward us compared to when it moves away. This bias illustrates EMT by showing how humans adaptively err on the side of caution in uncertain situations, potentially helping avoid dangers that are approaching.

Question 44

How does Error Management Theory (EMT) explain the sexual overperception bias observed in men?

Answer 44

EMT predicts that men have a sexual overperception bias, where they are more likely to misinterpret friendly gestures, like a smile, as signs of sexual or romantic interest.

This bias arises from the evolutionary cost of missing potential reproductive opportunities, leading men to err on the side of assuming sexual interest based on minimal cues. Empirical research, including studies with photographs, videotaped interactions, and speed dating, supports this adaptive bias.

Question 45

Define ​Sexual strategies theory

Answer 45

A comprehensive evolutionary theory of human mating that defines the menu of mating strategies humans pursue (e.g., short-term casual sex, long-term committed mating), the adaptive problems women and men face when pursuing these strategies, and the evolved solutions to these mating problems.