Chapter 3 Flashcards
the body’s building blocks
your body is made of cells, which are made of chromosomes, which are made of DNA, which are made of genes
genes–> DNA–> chromosome–> cell–> body
components of nature
genotype: inherited genetic material
phenotype: observable expression of the genotype ( body characteristics and behaviour)
genotype-phenotype-environment interactions: parents’ genotype influencing child’s genotype
- conception: get genetic material from partent at conception
- Random assortment: random assortment of chromosomes (which piece of each pair) goes to child
- Mutation: section of DNA/gene changes, may be due to random factors, in egg and/or sperm
- Sex determination: sex hormones, male (xx) or female (xy), sperm determines x or y from that pair and mom contributes x
genotype-phenotype-environment interactions: child’s genotype influencing child’s phenotype
developmental changes/timing
- reasons whiy certain genes may switch on and off
-how genes are being expressed
-some genes are active and others are dormant
dominance patterns
-homozygous
-heterozygous
-2 alleles per trait
– dominant and recessive
–uppercase= dominant
– lowercase= recessive
FF= dominant
Ff= dominant
ff= recessive
genotype-phenotype-environment interactions: child’s environment influencing child’s phenotype
diet (E) influencing expression (P) of genetic disorder (PKU for example)
presesnce of abuse (E) influencing expression (P) of MAOA gene (or any related gene, inactive gene means an increased chance of aggression)
job (E) influencing expression (P) of introversion
genotype-phenotype-environment interactions: child’s phenotype influencing child’s environment
personality (P) influencing response from people (E) –> extroverted child being given more opportunities to socialize
interests (P) being nurtured by environment (E)
genotype-phenotype-environment interactions: child’s environment influencing child’s genotype
environment can influence genes and turn them on and off
rat mothers: high lickers (kids will lick their kids) vs low lickers (kids won’t lick their kids)
epigenetics
life experiences influence how genes work, experience alters gene expression, even twins who share the same DNA will not share the same pattern of gene expression
what do genes code for
proteins
whether genes are expressed at all is a function of:
dominance patterns
what is crossing over
when gametes divide, the two members of a pair of chromosomes sometimes swap sections of DNA. As a result, some of the chromosomes that parents pass on to their offspring are constituted differently from their own.
what primarily controls the switching on and off of genes
regulator genes.
The activation or inactivation of one gene is always part of a chain of genetic events. When one gene is switched on, it causes another gene to turn on or off, which has an impact on the status of yet other genes. Thus, genes never function in isolation. Rather, they belong to extensive networks in which the expression of one gene is a precondition for the expression of another, and so on.
dominant- recessive pattern (discovered by Mendel)
Some genes have only two alleles, one of which is dominant and the other recessive. In this pattern, there are two possibilities:
(1) a person can inherit two of the same allele—two dominant or two recessive—and thus be homozygous for the trait in question;
or (2) the person can inherit two different alleles—one dominant and the other recessive—and thus be heterozygous for the trait.
When an individual is homozygous, the corresponding trait will be expressed. When an individual is heterozygous for a trait, the instructions of the dominant allele will be expressed
how many genes do the x and y chromosomes carry
x: roughly 1500 genes
y: roughly 200 genes
Thus, when a genetically female child inherits a recessive allele on the X chromosome from her genetically female parent, she is likely to have a dominant allele on the chromosome from her genetically male parent to suppress it, so she will not express the trait in question. In contrast, when a genetically male child inherits the same recessive allele on the X chromosome from his genetically female parent, he likely will not have a dominant allele from his genetically male parent to override it, so he will express the trait. Genetically male people are thus more likely than genetically female people to suffer a variety of sex-linked inherited disorders caused by recessive alleles on their X chromosome
Despite the traditional emphasis given to the dominant–recessive pattern of inheritance, it actually pertains to relatively few human traits—such as hair colour, blood type, abundance of body hair, and the like—as well as to a large number of congenital disorders
Behaviour geneticists try to tease apart genetic and environmental contributions by taking advantage of the differences observed amongst a population. Two premises underlie this endeavour:
(1) To the extent that genetic factors are important for a given trait or behaviour, individuals who are genotypically similar should be phenotypically similar; and
(2) to the extent that shared environmental factors are important, individuals who were reared together should be more similar than people who were reared apart.
twin study design
used to compare the correlations for identical (monozygotic, or MZ) twins with those for same-sex fraternal (dizygotic, or DZ) twins. For twins who grow up together, the degree of similarity of the environment is generally assumed to be equal. Known as the equal environments assumption, the claim is that both types of twins shared the same prenatal environment, were born at the same time (so experienced societal changes similarly), grew up in the same family and community, and are always the same age when tested. If the correlation between identical twins on a given trait or behaviour is substantially higher than that between fraternal twins, it is assumed that genetic factors are substantially responsible for the difference.
adoption study
In this approach, researchers examine whether adopted children’s scores on a given measure are correlated more highly with those of their biological parents and siblings or with those of their adoptive parents and siblings. Genetic influences are inferred to the extent that children resemble their biological relatives more than they do their adoptive ones.
heritability
a statistical estimate of how much of the measured variance on a phenotypic trait amongst individuals in a given population is attributable to genetic differences amongst those individuals.
a heritability estimate applies only to a particular population living in a particular environment
high heritability does not imply immutability. The fact that a trait is highly heritable does not mean that there is little point in trying to change it
studies of heritability to date primarily include samples of Western, educated, industrialized, rich, and democratic (WEIRD) participants
what are the basic units of the brain’s informational system
100 billion neurons, which constitute the grey matter of the brain.
three main components of the neuron
(1) a cell body, which contains the basic biological material that keeps the neuron functioning;
(2) dendrites, fibres that receive input from other cells and conduct it towards the cell body in the form of electrical impulses; and
(3) an axon, a fibre (anywhere from a few micrometres to more than a metre in length) that conducts electrical signals away from the cell body to connections with other neurons.
what are glial cells
essential component of the brain, equal in numbers to neurons
Glial cells perform a variety of critical functions, including the formation of a myelin sheath around axons, which increases the speed and efficiency of information transmission.
Glial cells also function as neural stem and progenitor cells during prenatal brain development, and some glial cells continue to do so into adulthood.
When the brain is injured, some glial cells react by rapidly increasing in numbers, protecting the brain and potentially aiding in regeneration.
how much of the human brain is made up of cerebral cortex
80%
The parts of the human cortex that are most enlarged compared with other species are also those that grow the most as children develop.
the four lobes of the cortex and their associated sets of behavioural characteristics
Starting at the back of the brain, the occipital lobe is primarily involved in processing visual information.
The temporal lobe is associated with speech and language, and the processing of emotion and auditory information.
The parietal lobe engages in spatial processing and is also involved in the integration of information from different sensory modalities.
The frontal lobe, the brain’s “executive,” is involved in cognitive control, including working memory, planning, decision-making, and inhibitory control.
where do the association areas lie and what info is processed and integrated
Information from multiple sensory systems is processed and integrated in the association areas that lie in between the major sensory and motor areas.
how do the two brain hemispheres communicate
The hemispheres communicate with each other primarily by way of the corpus callosum, a dense tract of connective nerve fibres between the two hemispheres.
neurogenisis
the proliferation of neurons through cell division, begins 42 days after conception (in humans) and is nearly complete by the midway point of gestation.
Thus, most of the roughly 100 billion neurons you currently possess have been with you since before you were born.
Notably, however, humans do continue to generate new neurons throughout life, particularly in the hippocampus—a brain area that is heavily involved in memory processes
neurogenesis is one of several ways in which experiences sculpt the brain.
what happens when neurons reach their destination
they first grow an axon and then a “bush” of dendrites. They take on the specific structural and functional characteristics of the different structures of the brain. Axons elongate as they grow towards their targets. The main change in dendrites is arbourization
what is arbourization
an enormous increase in the size and complexity of the dendritic “tree” that results from growth, branching, and the formation of spines on the branches.
Arbourization increases the dendrites’ capacity to form connections with other neurons.
As arbourization allows neurons to grow in complexity over the first several years of postnatal life, the cortex grows in surface area and the layers of the cortex become thicker
what is myelination
the formation of the insulating myelin sheath around some axons, begins prenatally and continues into early adulthood.
Atypical patterns of synaptic pruning have been implicated in two developmental disorders
autism spectrum disorder (ASD) and schizophrenia
experience-expectant plasticity
The role of species-typical experience in shaping brain development
Involves the general experiences that almost all infants have just by virtue of being human.
Experience-dependent plasticity
involves specific, idiosyncratic experiences that children have as a result of their particular life circumstances
Neural connections are constantly being created and reorganized by our specific experiences
Food preferences impact what we eat throughout life, and some of these preferences are innate. Infants display some of the same reflexive facial expressions that older children and adults display in response to basic tastes: sweet, umami (savoury), bitter, sour, and salty
The first two flavours produce positive responses: a hint of a smile, lip smacking, sucking. Bitter flavours elicit negative responses, including frowning and nose wrinkling.
Sour flavours elicit varied responses: some infants respond negatively while others respond positively.
Salty flavours do not elicit much of a reaction until after 4 months of age, when a preference for salt emerges.
The influence of environmental factors is particularly evident in secular trends, marked changes in physical development that have occurred over generations
adults are several inches taller than their ancestors
girls, on average, begin menstruating a few years earlier than their ancestors.
why do newborns prefer sweet flavours
they will drink larger quantities of sweetened water than plain water.
These preferences may have an evolutionary origin, because poisonous substances are often bitter or sour but almost never sweet
neophobia
an unwillingness to eat unfamiliar foods. Avoidance of unknown foods likely evolved as an adaptive response, helping to keep children safe (especially important given infants’ and toddlers’ propensity to put everything they find in their mouths).
why is BMI unreliable with kids
may be less reliable as a measure of body fat when used specifically for children because it fails to take into account muscle mass and pubertal development, both of which are highly variable across childhood and early adolescence
Environmental factors that promote childhood obesity
unhealthy school lunches, less time playing outside, more screentime, less sleep, screens in room
innovative approach is being implemented in Vanuatu for vaccinations
About 20% of the children in Vanuatu do not receive all of their vaccinations due to the remoteness of villages and lack of electricity. To address this problem, UNICEF funded a program to deliver vaccines by drone. Each drone can hold a 5-pound pack of vaccines packaged in ice and can fly 30 miles to villages that are difficult to reach by road or sea. This program represents a clever use of modern technology to deliver lifesaving vaccines, and it was implemented more recently to deliver COVID-19 vaccines to remote locations in India and other countries.
system of interventions implemented in Nepal
Nearly 50,000 women travel the country to deliver basic health care, treating common childhood infections such as diarrhea and pneumonia. With their help, Nepal became the first country to deliver vitamin A supplements every 6 months to children nationwide. And because the volunteers are spread throughout the country, they are able to intervene rapidly. Volunteers arrive shortly after births, prepared to detect and help manage low-birth-weight neonates. While this program faces challenges—many of the volunteers are illiterate, requiring them to depend on memory about treatments and family histories, and the long walks between villages can hamper opportunities for training—it has also dramatically improved outcomes for children’s nutritional and physical health. Community health volunteer programs have been established in developing countries across Asia and Africa, where they also provide prenatal and postnatal health care, vaccinations, disaster relief, and other medical services.
