Module 2 Flashcards
(Module Notes AND Textbook Chapter)
1
Q
Each one of us originated from what two germ cells?
A
A sperm and an ovum.
2
Q
How are germ cells produced?
A
Through meiosis.
3
Q
Define meiosis.
A
The cell division process that results in a germ cell containing 23 chromosomes.
4
Q
True or False?
Females are born with all of their ovum, whereas males make sperm continuously.
A
True.
5
Q
During conception, an average of how many sperm are released into the female and make their journey to attempt to fertilize the egg?
A
500 million.
(the sperm must swim for 6-7 hours to reach their destination.)
6
Q
From the initial 500 million candidates, only about __________ sperm actually get close to the egg.
A
200.
7
Q
Some sperm fail to reach the egg due to chance factors, while others fail due to _________.
A
Genetic defects.
8
Q
Where does fertilization of the egg normally occur?
A
In the upper third portion of the fallopian tube.
9
Q
What is a zygote?
A
A fertilized egg cell.
(Prenatal development has begun.)
10
Q
Prenatal development is broken into what 3 main stages?
A
1) The germinal period (weeks 0-2)
2) The embryonic period (weeks 3-8)
3) The fetal period (weeks 9-birth)
11
Q
What happens during the germinal period (the first 2 weeks of development)?
A
The zygote is rapidly dividing. Approximately 4-5 days after fertilization, the zygote enters the uterus from the fallopian tube. The zygote is now referred to as the blastocyst – it forms as a hollow ball of cells and will implant into the wall of the uterus. The germinal period comes to an end when the blastocyst is fully embedded, which takes about one week.
12
Q
What happens during the embryonic period (implantation to 8 weeks)?
A
Cell differentiation begins and the beginnings of all organ systems are forming. Embryonic development follows a cephalocaudal pattern of development, meaning that areas near the head tend to develop first. By the end of the embryonic period, all bodily systems are functioning.
13
Q
What are some key features of the embryonic period?
A
1) Three layers of cells differentiate:
Ectoderm: The ectoderm will become the nervous system, nails, teeth, inner ear, eye lens, and epidermis.
Mesoderm: The mesoderm will become muscles, bones, circulatory system, and skin.
Endoderm: The endoderm will become the digestive system, lungs, urinary tract and glands.
2) Nervous System Development - The neural tube also forms during this period, which is the precursor to the Central Nervous System. The neural tube is created when the ectoderm folds in on itself, creating a u-shaped groove.
3) Embryo Support System - This includes the amniotic sac (a liquid-filled sac in which the embryo floats, helping to protect it and maintain a constant temperature) and the placenta (which has numerous functions, including allowing nutrients, oxygen, and waste to pass through, while at the same time preventing maternal blood from mixing with the blood of the developing embryo.)
14
Q
What happens during the fetal period (weeks 9-birth)?
A
Development continues to be rapid and cephalocaudal in nature. Around 11-12 weeks, the fetus starts to become more active (spontaneous movements, reflexes) although movements are not felt by the mother until the fetus becomes larger, usually around 16 weeks. By 20 weeks, the fetus starts to have facial expressions and begins putting on weight.
15
Q
____________ weeks is considered the age of viability (the point at which the brain and lungs are developed enough for survival without major medical intervention).
a) 28 weeks
b) 23 weeks
c) 21 weeks
d) 24 weeks
A
b) 23 weeks.
16
Q
True or False?
An active fetus is likely to become an active newborn.
A
True.
Fetal movement helps promote muscle development. Interestingly, there are large individual differences in prenatal activity, with these differences continuing into infancy. In other words, an active fetus is likely to become an active newborn.
17
Q
A fetus experiences some degree of sensory input from all five senses, although __________ input is minimal.
A
Visual.
18
Q
Since a fetus can move around, it can experience ________ sensations such as kicking the walls of the uterus.
A
Tactile.
19
Q
True or False?
Amniotic fluid contains both odours and flavours (related to what the mother ingests), which a fetus can smell and taste.
A
True.
Researchers suspect that this may be one way in which cultural flavour preferences are transmitted.
20
Q
A fetus can hear the world around them. This includes both the _______ world (e.g., mom’s heartbeat) and the _______ world (e.g., voices of their family members).
A
maternal, outside
21
Q
When discussing fetal learning, we are only considering learning in its most simple form - and ___________.
A
habituation and dishabituation
(Researchers examine whether a fetus gets “bored” of a stimulus and if interest peaks when the stimulus is changed. Indeed, research suggests that the nervous system of a fetus is developed enough to engage in this type of basic learning (e.g., they habituate to repeated stimuli). A fetal brain, however, is not yet developed enough to engage in more complex forms of learning.)
22
Q
Which of the following statements is NOT true about the period of the embryo?
a) It begins when the developing organism is fully implanted in the uterine wall.
b) It lasts from weeks 3-8 of a pregnancy.
c) All of the major organ systems are functioning before the end of this period.
d) All of the major organ systems are fully integrated with one another before the end of this period.
A
d) All of the major organ systems are fully integrated with one another before the end of this period.
23
Q
What period of prenatal development last between 3-8 weeks?
A
The Embryonic Period.
24
Q
What is a teratogen?
A
An external agent that can cause damage or death during prenatal development. (textbook definition)
Anything that has an adverse impact on development. (module definition)
25
List some examples of teratogens.
Chemicals
Medications
Recreational Drugs
Alcohol and Nicotine
Some Viruses and Bacteria
Maternal Health
26
The impact that a given teratogen will have on a developing fetus depends on many factors. List some of these factors.
Type of Teratogen
Dosage
Duration of Exposure
Timing of Exposure
Genetics of the Mother
Genetics of the Fetus
27
What is one of the most infamous teratogens?
Thalidomide - a medication that was approved for pregnant women without proper testing. Thalidomide resulted in serious birth defects for newborns who were exposed in utero.
28
____________ during pregnancy is one of the leading causes of preventable birth defects and developmental disabilities.
Alcohol use.
29
Exposure to teratogens during the ___________ period can result in major structural abnormalities.
(For example, exposure to alcohol can have significant impacts on major systems like the CNS.)
Embryonic.
30
Teratogen exposure during the _____________ period is more likely to result in physiological defects or minor structural abnormalities.
Fetal.
(Major structural defects are less likely in the fetal period because the basic organ systems are already in place.)
31
Not all pregnancies with such teratogen exposures will result in birth defects. What are 2 reasons why?
1) First, there is a dose-response relationship between exposure to teratogens like these and the likelihood of negative outcomes. In other words, the higher the dose, the greater the likelihood of negative outcomes.
2) Second, both maternal and fetal genetic susceptibilities (e.g., variation in the rate a drug will be metabolized) influence the final outcome.
32
Longitudinal research indicates that children exposed to cannabis early in development are at a greater risk for attention deficits, increased hyperactivity, and increased likelihood of _________.
substance use.
33
Which of the following statements is most true about the effect of alcohol on the developing baby?
a) The more mothers drink, the more likely it is to have an effect on their child; however, some babies will be unaffected due to their mother's and/or their own genetic endowments.
b) The more mothers drink, the more likely it is to have an effect on their child; however, some babies will be unaffected due to the mother's genetic endowments.
c) Babies will only be affected by mothers who drink in the last trimester.
d) All babies will be affected equally by mother's drinking.
a) The more mothers drink, the more likely it is to have an effect on their child; however, some babies will be unaffected due to their mother's and/or their own genetic endowments.
34
Which of the following are teratogens?
Alcohol
Sunshine
Cocaine
Phenytoin (Seizure medication)
Sushi
Varicella (Chickenpox)
Maternal exercise
Alcohol, Cocaine, Phenytoin (Seizure medication), Varicella (Chickenpox)
35
Every cell in your body contains chromosomes. Humans have _____ chromosomes, divided into _____ pairs.
46, 23
(We obtained one pair of chromosomes from each of our parents through meiosis.)
36
Chromosomes are made up of _____________.
DNA (deoxyribonucleic acid).
37
DNA carries all of the “instructions” for making a person, which are packaged in genes. Importantly, genes code for __________, NOT for specific behaviors.
proteins
(Proteins are the key ingredient that determines a cell’s characteristics and functions.)
38
What are alleles?
Different forms of the same gene. This “back up copy” is helpful to ensure proper development.
39
Very few human traits follow basic Mendelian patterns. In other words, _____________ is responsible for most human traits.
polygenic inheritance
40
Define genotype.
The genetic material an individual inherits.
41
Define phenotype.
The observable expression of the genotype, including both body characteristics and behaviour.
42
What do epigenetic “markers” do?
They control where and how much protein is made by a gene, effectively turning the gene “on” or “off”.
This occurs naturally during prenatal development when cells are differentiated (e.g., one cell becomes a brain cell while another becomes skin). It also occurs from environmental influences. Where you live, what you eat, who you interact with, and what you do in daily life impacts your gene expression. In other words, environmental experiences leave “marks” on our genetic information that changes how they are expressed
43
What is the study of behavioural genetics?
The study of how nature and nurture contribute to behaviour.
Specifically, behavioural genetics tries to determine how much variation in behaviour is the result of environmental versus genetic factors.
44
What is a twin study?
It compare monozygotic (identical, 100% genetic similarity) twins to dizygotic (fraternal, 50% genetic similarity) twins.
Researchers typically assume that the twins were raised in the same environment. This is one reason why dizygotic twins are used instead of siblings, as dizygotic twins have more similarity in their environment (starting from the womb!).
45
What is an important limitation in twin studies?
Even for twins, their environment is rarely 100% shared. For example, consider twins who might be in different classrooms at school – these children would have different teachers and different friendships.
46
What is an adoption study?
It looks to see if offspring become more similar to their biological parents or to their adoptive parents.
If they become more similar to their adoptive parents on a given trait (e.g., reading ability), we can assume there is an environmental contribution. On the other hand, if the children become more similar to their biological parents on a given trait (e.g., shyness), w
47
What is an important limitation in adoption studies?
There is little environmental variation in adoptive families. Most adoptive families are in the middle-class, so it is difficult to disentangle environmental and genetic influences in high-risk environments.
48
Define heritability of traits.
The percentage of variance in a population due to genes.
49
Heritability estimates range from 0-1. What does 0 mean? What does 1 mean?
0 means the variation in a trait is completely due to environmental factors.
1 means that 100% of the variation in a trait is completely due to genetic factors.
50
True or False
Heritability and heredity are the same thing.
False.
Heredity is the passing of traits from children to offspring, whereas heritability is a statistic looking at the proportion of variance in a trait that is due to genetics.
51
Heritability is measure at what level?
a) Individual
b) Population
b) Population.
A heritability estimate of .40 for shyness does NOT mean that 40% of your variability in shyness is from your parents. Heritability only talks about populations, not individuals.
52
Heritability is __________. It tells us nothing about the specific genes or environmental factors that contribute to behaviour.
abstract
53
Genes code for:
a) Traits
b) Behaviours
c) DNA
d) Proteins
d) Proteins.
(Remember - Proteins are they key ingredient that determines a cell’s characteristics and functions. )
54
Which of the following is NOT true about heritability?
a) Because we know that mental health conditions like Autism are heritable, we know all of the specific genes that contribute to this disease.
b) Heritability estimates range from 0-1. For example, height has a heritability of ~.80.
c) Heritability works at the population level, so we cannot say how much of a certain behaviour you inherited from your parents.
d) The degree of heritability for a given trait depends on the population and environment we are considering.
a) Because we know that mental health conditions like Autism are heritable, we know all of the specific genes that contribute to this disease.
55
Describe Neurogenesis.
The process through which new neurons are formed in the brain.
Begins 3-4 weeks after conception, generally ends by weeks 18-20.
At its peak, 250,000 neurons are formed each minute.
56
Describe Neural Migration.
The process by which neurons migrate, or move, to their adult location in the brain.
6-24 weeks after conception.
Neurons migrate using both active and passive movement – some actively propel themselves, while others are carried along passively.
57
Describe Myelination.
3rd trimester-adulthood
Once in their final destination, neurons continue to grow and differentiate. They also develop their myelin sheath – myelination is the process by which the myelin sheath (fatty sheath) forms around the axons of neurons.
The myelin sheath increases the speed of neural transmission and increases information-processing abilities in the brain.
58
Describe Synaptogenesis.
3rd trimester-adulthood
Once grown and developed, neurons start “talking” to each other through synapses. Synaptogenesis is the process through which neurons form synapses with other neurons, resulting in trillions of connections.
59
Describe Synaptic Pruning.
Occurs throughout development, with bursts in early development and during adolescence.
Synaptic pruning is a normal developmental process through which certain synapses are eliminated. About 40% of the synapses that develop are eventually eliminated. Pruning occurs in different areas of the brain depending on development. Gray matter becomes less dense as the brain matures. The prefrontal cortex, which controls executive functioning and long-term planning, is the last to mature.
60
Why does (synaptic) pruning happen?
It is an evolutionary advantage to have a changeable brain – this allows organisms to adapt to their environment and survive in changing conditions.
61
What is plasticity?
Plasticity reflects the capacity of the brain to be affected by experience. Plasticity is just another way the environment interacts with an organism to influence their development.
62
What are the 2 types of plasticity?
1) Experience-Expectant
2) Experience-Dependant
63
What is Experience-expectant plasticity?
It involves normal wiring of the brain and occurs in part from typical, expected experiences. For example, hearing sounds and language is an expected part of development, and helps to develop associated brain areas. If this doesn’t happen, these brain regions do not develop in typical ways and will be taken over by other sensory areas.
Relatedly, experience-expectant plasticity is associated with the concept of sensitive periods. These are specific times when the brain requires a specific form of experience. For example, the infant brain is wired to be responsive to language. If an infant is not exposed to language early in development, it is much more difficult for language capacities to develop in the brain
64
What is Experience-dependant plasticity?
The process by which neural connections are created/reorganized based on an individual’s personal experience.
This type of plasticity is related to learning and memory and occurs throughout the lifespan. For example, London taxi drivers have highly developed hippocampi, the area of the brain involved in memory. This is thought to be caused by their experiences driving and memorizing the complex roadways in London.
65
Leo is an avid drum player. He plays the drums throughout his childhood and becomes a professional drummer as an adult. What might we expect about Leo's brain development?
a) Leo's brain develops in ways similar to his family due to genetics.
b) The connections in Leo's brain that are involved in playing the drums (e.g., motor control) were strong until puberty, but then were destroyed due to pruning.
c) The connections in Leo's brain that are involved in playing the drums (e.g., motor control) are strong, which is different than someone who did not grow up playing the drums like Leo.
d) Playing the drums has no impact on Leo's brain development
c) The connections in Leo's brain that are involved in playing the drums (e.g., motor control) are strong, which is different than someone who did not grow up playing the drums like Leo.
66
Define epigenesis.
The emergence of new structures and functions in the course of development.
67
What are gametes (germ cells)?
Reproductive cells—egg and sperm—that contain only half the genetic material of all the other cells in the body.
68
Define conception.
The union of an egg from the mother and a sperm from the father.
69
True or False?
The egg is the largest human cell (the only one visible to the naked eye), but sperm are among the smallest.
True.
70
True or False?
For decades, and across many cultural contexts, infant mortality rates have been higher for boys than for girls.
True.
During labour and delivery, males are more likely to experience fetal distress than females, even controlling for the males’ larger size and head circumference .
Male fetuses are more sensitive than females are to teratogens (harmful external agents), including opioids and alcohol, which affects their viability and ability to thrive after birth. Male infants’ heightened vulnerability is not limited to the immediate postnatal period. Males are also more likely than females to die from SIDS, and have higher rates of incidence of a wide range of developmental disabilities, including attentional disorders and autism spectrum disorders.
71
True or False?
There are slightly more male newborns (51.3%) across generations and around the world.
True.
This is the case, despite the fact that male fetuses are more susceptible to spontaneous abortion than females in both the 1st week and last several weeks of pregnancy (though it is worth noting that female fetuses are more susceptible in weeks 10–15).
72
What 4 major developmental processes underlie the transformation of a zygote into an embryo and then a fetus?
1) Mitosis - cell division that results in two identical cells.
2) Cell Migration - the movement of newly formed cells away from their point of origin. (Ie: neurons that originate deep inside the embryonic brain and then travel to the outer reaches of the developing brain.)
3) Cell Differentiation - all of the embryo’s cells can give rise to any of the more than 200 possible cell types in the human body. After several cell divisions, however, these cells start to specialize.
4) Death - apoptosis (genetically programmed cell death). Ie: he formation of fingers depends on the death of the cells in between the ridges in the hand plate. Death is preprogrammed for the cells that disappear from the hand plates.
73
What is the difference between an embryo and a fetus?
Embryo - term for the developing organism from the 3rd to 8th week of prenatal development.
Fetus - term for the developing organism from the 9th week to birth.
74
What are embryonic stem cells?
Embryonic cells, which can develop into any type of body cell.
75
__________ play a crucial role in sexual differentiation.
Hormones.
(The presence of androgens, a class of hormones that includes testosterone, leads to the development of male genitalia. If androgens are absent, female genitalia develop. The source of androgens is the male fetus itself, at around the 8th week after conception. This is just one of the many
ways in which the fetus influences its own development.)
76
On its journey through the fallopian tube to the womb, the zygote doubles its number of cells roughly _______ a day.
twice
77
By the _____ day after conception, the cells arrange themselves into a hollow sphere with a bulge of cells, called the inner cell mass, on one side.
4th
78
What are identical (monozygotic) twins?
Twins that result from the splitting in half of the zygote, resulting in each of the two resulting zygotes having exactly the same set of genes.
79
What are fraternal (dizygotic) twins?
Twins that result when two eggs happen to be released into the fallopian tube at the same time and are fertilized by two different sperm; fraternal twins have only half their genes in common.
80
What is the neural tube?
A groove formed in the top layer of differentiated cells in the embryo that eventually becomes the brain and spinal cord.
81
The inner cell mass (that becomes the embryo) is initially a single layer thick, but during the 2nd week, it folds itself into three layers, each with a different developmental destiny.
The top layer becomes ________________________.
The middle layer becomes _______________________.
The bottom layer develops into ___________________.
Top layer: the nervous system, the nails, teeth, inner ear, lens of the eyes,
Middle layer: muscles, bones, the circulatory system, the inner layers of the skin, and other internal organs.
Bottom layer: the digestive system, lungs, urinary tract, and glands.
82
What is the amniotic sac?
A transparent, fluid-filled membrane that surrounds and protects the fetus.
83
What is the placenta?
A support organ for the fetus; it keeps the circulatory systems of the fetus and mother separate, but a semipermeable membrane permits the exchange of some materials between them (oxygen and nutrients from mother to fetus, and carbon dioxide and waste products from fetus to mother)
84
Roughly how much does the placenta weight?
One pound.
85
True or False?
While we might assume that the placenta comes from the fetus, 90% of the cells in the placenta come from the mother.
False.
It's the other way around:
While we might assume that the placenta comes from the mother, 90% of the cells in the placenta come from the fetus itself.
86
What is the umbilical cord?
A tube containing the blood vessels connecting the fetus and placenta.
87
What is cephalocaudal development?
The pattern of growth in which areas near the head develop earlier than areas farther from the head.
88
What is phylogenetic continuity?
The idea that because of our common evolutionary history, humans share many characteristics, behaviours, and developmental processes with non-human animals, especially mammals.
89
The noise level in the uterus ranges from about ___ - ______ decibels (roughly the noise level of a vacuum to a lawnmower)..
70–95 decibels (roughly the noise level of a vacuum to a lawnmower).
90
Define habituation.
A simple form of learning that involves a decrease in response to repeated or continued stimulation.
91
Define dishabituation.
The introduction of a new stimulus rekindles interest following habituation to a repeated stimulus.
92
What is a sensitive period?
The period of time during which a developing organism is most sensitive to the effects of external factors.
93
What is fetal programming?
It refers to the belated emergence of effects
of prenatal experience that “program the physiological set points that will govern physiology in adulthood”.
94
The effects of teratogens can also vary according to individual differences in genetic susceptibility. Thus, a substance that is harmless to most people may trigger problems in individuals whose genes predispose them to be affected by it. Identifying teratogens is further complicated by the existence of ____________, in which the impact of a given agent may not be apparent for many years.
sleeper effects
95
What is Neonatal abstinence syndrome (NAS)?
A form of drug withdrawal seen when fetuses exposed to opioids in the womb are born.
96
The main developmental consequences of maternal smoking are _______ and ____________.
slowed fetal growth and low birth weight
(In addition, smoking is linked to increased risk of SIDS and a variety of other problems, including lower IQ, hearing deficits, ADHD, and cancer.)
97
In Canada, SIDS accounts for ______ (what percentage) of postneonatal deaths, making it the leading cause of infant mortality between 28 days and 1 year of age.
21.3%
98
What is sudden infant death syndrome (SIDS)?
The sudden, unexpected death of an infant less than 1 year of age that has no identifiable cause.
99
To decrease the risk of SIDS, the most important steps that parents can take entail removing any barriers to their baby’s ________.
Breathing.
100
_________ increases the risk of SIDS more than any other single factor.
Sleeping on the stomach
101
When a pregnant woman drinks, the alcohol in her blood crosses the placenta into both the fetus’s bloodstream and the __________________.
Amniotic fluid.
(Thus, the fetus gets alcohol both directly—in its bloodstream—and indirectly, by drinking an amniotic-fluid cocktail. Concentrations of alcohol in the blood of mother and fetus quickly equalize, but the fetus has less ability to metabolize and remove alcohol from its blood, so it remains in the fetus’s system longer.)
102
What is fetal alcohol spectrum disorder (FASD)?
the harmful effects of maternal alcohol consumption on a developing fetus. Fetal alcohol syndrome (FAS) involves a range of effects, including facial deformities, intellectual disabilities, attention problems, hyperactivity, and other defects.
Fetal alcohol effects (FAE) is a term used for individuals who show some, but not all, of the standard effects of FAS.
103
Effects of maternal stress during pregnancy have been observed on myriad aspects of infant and child development, ranging from infant cognitive development to later psychiatric diagnoses. Brain-imaging studies with infants and young children reveal both structural and functional effects of prenatal maternal state on the developing brain.
A primary mechanism for these effects is alternations in the _________________ axis and the hormone ___________, a glucocorticoid which helps regulate stress in both the mother and the fetus.
hypothalamic–pituitary–adrenal (HPA) axis, cortisol
104
Genetic factors may also link both maternal stress and postnatal outcomes. One clever study took advantage of the increased use of IVF to attempt to tease apart these factors. In this study, mothers were either genetically related or unrelated to their fetuses. What did the results show?
The results revealed effects of maternal stress on birth weight and later antisocial behaviour, in both related and unrelated mother–fetus pairs, suggesting that the prenatal environment, not shared genetics, was the strongest predictor of later outcomes. However, for measures of child anxiety, the results suggest that postnatal maternal stress, not prenatal maternal stress, was the strongest predictor of later outcomes.
105
Define genome.
the complete set of DNA of any organism, including all of its genes.
106
Genotype, phenotype and environment are involved in what five relations that are fundamental in the development of every child?
(1) parents’ genetic contribution to children’s genotypes;
(2) the contribution of children’s genotypes to their own phenotypes;
(3) the contribution of children’s environments to their phenotypes; (4) the influence of children’s phenotypes on their environments;
(5) the influence of children’s environments on their genotypes.
107
The nucleus of every cell in the body contains __________, long threadlike molecules made up of two twisted strands of _______. ________ carries all the biochemical instructions involved in the formation and functioning of an organism. These instructions are “packaged” in __________, the basic unit of heredity in all living things.
chromosomes, DNA, DNA, genes
108
Each gene is a segment of DNA that is the code for the production of particular proteins. Some proteins are the building blocks of the body’s cells; others ______ the cells’ functioning.
regulate
109
Define DNA (deoxyribonucleic acid).
molecules that carry all the biochemical instructions involved in the formation and functioning of an organism
110
Define genes.
sections of chromosomes that are the basic unit of heredity in all living things
111
What is the process of crossing over?
The process by which sections of DNA switch from one chromosome to the other; crossing over promotes variability among individuals
112
What are two mechanisms that promotes variability among individuals?
1) Random assortment of chromosomes in the formation of egg and sperm. During gamete division, the 23 pairs of chromosomes are shuffled randomly, with chance determining which member of each pair goes into each new egg or sperm. When a sperm and an egg unite, the odds are essentially zero that any two individuals—even members of the same family—will have the same genotype (except, of course, identical twins). Further variation is introduced by a process called crossing over.
2) Mutation - a change in a section of DNA. Some mutations are random, spontaneous errors; others are caused by environmental factors. Those that occur in gametes (germ cells) can be passed on to offspring. Many inherited disorders originate from a mutated gene.
113
True or False?
Most mutations (a change in a section of DNA) are harmful.
True.
Occasionally, however, a mutation enhances the individual’s genetic fitness by increasing disease resistance or allowing the individual to adapt to some crucial aspect of the environment. Such mutations provide the basis for evolution: individuals with the favourable mutated gene are more likely to survive long enough to produce offspring, who, in turn, are likely to possess the mutated gene, thus heightening their own chance of surviving and reproducing.
114
What are sex chromosomes?
The chromosomes (X and Y) that determine an individual’s designated sex at birth.
115
Why are sex chromosomes (which determine an individual’s designated sex at birth) an exception to the general pattern of chromosome pairs?
Genetic females have two identical, largish sex chromosomes called X chromosomes, but genetic males have one X chromosome and one much smaller Y-shaped chromosome. Because a female has only X chromosomes, the division of her germ cells results in all her eggs having an X. However, because a male is XY, half his sperm contain an X chromosome and half contain a Y.
For this reason, the genetically male parent always determines the genetic sex of offspring.
116
What are endophenotypes?
Intermediate phenotypes, including the brain and nervous systems, that do not involve overt behaviour.
117
The switching on and off of genes is controlled primarily by ________ genes.
regulator
118
True or False:
Genes function in isolation.
False.
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.
119
What are 2 examples of external factors that can affect the switching on and off of genes?
1) The effect of thalidomide on limb development, in which the sedative interferes with the functioning of genes underpinning normal growth factors.
2) Vision: early visual experience is necessary for the normal development of the visual system because it causes the switching on of certain genes, which, in turn, switch on other genes in the visual cortex. The ramifications of decreased visual experience are observed in cases of children with cataracts that are not removed early in life.
120
Many of an individual’s genes are never expressed; some others are only partially expressed. What factor determines whether a gene is expressed?
One-third of human genes have two or more different forms, known as alleles.
The alleles of a given gene influence the same trait or characteristic (e.g., eye colour), but they contribute to different developmental outcomes (e.g., brown, blue, hazel, gray eyes).
121
Perhaps the simplest pattern of gene expression—discovered by ________ —is referred to as the dominant–recessive pattern.
Mendel
122
What is the dominant allele?
the allele that, if present, gets expressed
123
What is the recessive allele?
the allele that is not expressed if a dominant allele is present
124
Define homozygous.
having two of the same allele for a trait
125
Define heterozygous.
having two different alleles for a trait
126
Flip to see an explanation of the dominant-recessive pattern.
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
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True or False?
Genetic males are thus more likely than females to suffer a variety of sex-linked inherited disorders caused by recessive alleles on their X chromosome.
True.
(The X chromosome carries roughly 1,500 genes, whereas the much smaller Y chromosome carries only about 200. Thus, when a genetic female inherits a recessive allele on the X chromosome from her mother, she is likely to have a dominant allele on the chromosome from her father to suppress it, so she will not express the trait in question. In contrast, when a genetic male inherits the same recessive allele on the X chromosome from his mother, he likely will not have a dominant allele from his father to override it, so he will express the trait.)
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Despite the traditional emphasis given to the dominant–recessive pattern of inheritance, it actually pertains to relatively few human traits. List a few of those traits.
hair colour, blood type, abundance of body hair, and the like—as well as to a large number of genetic disorders.
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Define polygenic inheritance.
Inheritance pattern in which traits are governed by more than one gene.
(For example, the variability in human intelligence is currently believed to be linked to more than 500 different genes)
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One example of a phenotype produced by a genotype–environment interaction is phenylketonuria (PKU). What is PKU?
A disorder related to a defective recessive gene on chromosome 12 that prevents metabolism of the amino acid phenylalanine.
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How is PKU an example of a how the child's environment can affect their phenotype?
Individuals who inherit this gene from both parents cannot metabolize phenylalanine, an amino acid present in many foods (especially red meats) and in aspartame, an artificial sweetener. If they eat a normal diet, phenylalanine accumulates in the bloodstream, causing impaired brain development and intellectual disabilities. However, if infants
with the PKU gene are identified shortly after birth and kept on a stringent diet free of phenylalanine, intellectual impairment can be avoided. Thus, a given genotype results in very different phenotypes —intellectual disability or relatively normal intelligence—depending on environmental circumstances.
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What is carrier genetic testing?
Genetic testing used to determine whether prospective parents are carriers of specific disorders.
For example, carrier genetic testing is typically offered to people of Eastern European Jewish descent because they have an increased likelihood of carrying the recessive gene for Tay Sachs, a severe birth defect that culminates in death by age 5. Or to people of African descent because they have an increased likelihood of carrying the recessive gene for sickle-cell disease, in which red blood cells have an atypical sickle shape causing chronic anemia and pain.
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What is preimplantation genetic diagnosis?
Fertilized eggs are tested for a specific genetic disorder in the IVF process. Eggs that do not carry the gene are chosen for implantation into the mother’s uterus.
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What is prenatal testing?
Genetic testing used to assess the fetus’s risk for genetic disorders.
(For example, non-invasive prenatal testing (NIPT) uses fragments of fetal DNA that enter the mother’s bloodstream to test for aneuploidy (missing or extra chromosomes), which is associated with conditions such as trisomy 13 (Patau syndrome), trisomy 18 (Edwards syndrome), and trisomy 21 (Down syndrome), depending on the location of the aneuploidy. More invasive prenatal diagnostic tests detect genetic anomalies using fetal cells, either from the placenta (chorionic villus sampling, or CVS, usually done between 10 and 13 weeks of pregnancy) or from amniotic fluid (amniocentesis, usually done between 15 and 20 weeks of pregnancy).
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What does newborn screening involve?
Tests used to screen newborn infants for a range of genetic and non-genetic disorders.
(Newborns receive a tiny pinprick to their heel to get a blood sample, which is then tested for 30 to 50 different genetic and non-genetic disease biomarkers, including PKU.)
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What is the MAOA gene?
An X-linked gene that inhibits brain chemicals associated with aggression.
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Parents’ own genetic makeup influences the environment parents provide for their children. These types of gene–environment correlations are observed frequently in the study of child development. Give an example of this.
Parents for whom reading is challenging—perhaps related to genetic factors, such as reading disabilities like dyslexia, which are known to be highly heritable (and highly polygenic)—are less likely to provide a reading- oriented environment for their children than parents who are skilled readers.
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What is the genetic nurture phenomenon?
Non-transmitted parental alleles play an important role in the creation of the child’s environment.
For example, researchers characterized the genotypes of trios—a child and their two biological parents—and found that the child’s educational outcomes were predicted, in part, by parental alleles that the child did not inherit. By affecting the parents’ phenotypes (and thereby influencing the family environments), the parents’ genes affected their children’s educational success.
139
True or False?
The genotype is “fixed” at conception.
False.
Geneticists previously believed that the genotype was “fixed” at conception. The field of epigenetics has turned this conventional wisdom on its head. Although the structure of the genetic code remains “fixed” during one’s lifetime, the expression of the genetic code is altered.
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Define epigenetics.
The study of stable changes in gene expression that are mediated by the environment.
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What is the epigenetic mechanism most commonly studied in humans?
Methylation - which silences gene expression.
142
Define behaviour genetics.
The science concerned with how variation in behaviour and development results from the combination of genetic and environmental factors.
143
Define heritable
Refers to characteristics or traits that are genetically transmitted.
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Behaviour geneticists try to tease apart genetic and environmental contributions by taking advantage of the differences observed among a population. What 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.
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The mainstay of quantitative behaviour genetics is the _______ study, which attempts to determine whether phenotypic traits are correlated with the degree to which people are genetically related—parents and children, identical and fraternal twins, non-twin siblings, or adoptive family members.
family
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What is 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.
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What is chorionicity?
Among MZ twin pairs, there are notable differences in the degree of placental sharing.
145
Define heritability.
A statistical estimate of the proportion of the measured variance on a trait among individuals in a given population that is attributable to genetic differences among those individuals.
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True or False?
Identical (MZ) twins resemble each other in IQ more than do same-sex fraternal (DZ) twins.
True.
(At the same time, environmental influences are reflected in the fact that identical twins are not identical in terms of IQ. Further evidence for the influence of environmental factors is that MZ twins reared together are more similar than those reared apart.)
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As compelling as they seem, heritability measures have also been widely criticized. Where does part of the criticism stem from?
1) The term “heritability” is often misinterpreted or misused by the public. The concept of heritability is commonly (and mistakenly) applied to individuals, despite the fact that, as we have emphasized, heritability applies only to populations. (Ie: The heritability of intelligence is generally considered to be approximately 50%. This means that, for the population studied, roughly 50% of the variation in IQ scores is due to genetic differences among the members of the population. It does not mean that 50% of your IQ score is due to your genetic makeup and 50% is due to your experience.)
2) A heritability estimate applies only to a particular population living in a particular environment. Consider the case of height. (Ie: Research conducted almost exclusively with North Americans and Europeans—most of them adequately nourished—puts the heritability of height at around 90%. But what if some segment of this population had experienced a severe famine during childhood, while the rest remained well fed? Would the heritability estimate for height still be 90%? No—because the variability due to environmental factors (poor nutrition) would increase dramatically; therefore, the variability that could be attributed to genetic factors would decrease to the same degree.)
3) Another common misperception is that heritability estimates are inherent to the trait in question and are not affected by the context in which the trait is measured. But heritability estimates necessarily reflect the environments of the populations of individuals from which they are derived. (Ie: Consider hypothetical heritability estimates of reading ability for children in two different countries: Brazil, where there is considerable variability in educational opportunities, and Finland, where nearly all children have excellent educational opportunities (Bishop, 2015). The heritability estimate of reading ability for children in Brazil would likely be much lower than in Finland. For children in Brazil, individual differences in reading outcomes will be more heavily influenced by the environment because educational experiences are far more variable than in Finland. Thus, heritability estimates may appear larger within populations with more homogeneous environments.)
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True or False?
Heritability estimates can change as a function of
developmental factors.
True.
Even for the same trait in the same population. Sometimes these patterns are counterintuitive. For instance, as twins get older, the degree of variance in intelligence accounted for by their genetic similarity actually increases. These results are consistent with the idea that people actively construct their own environment.
149
True or false?
High heritability implies immutability.
False.
It does NOT imply immutability. The fact that a trait is highly heritable does not mean that there is little point in trying to improve the course of development related to that trait. For example, the fact that the heritability estimate for IQ is relatively high does not mean that the intellectual performance of young children living in poverty cannot be improved by appropriate intervention efforts.
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Finally, studies of heritability to date primarily include samples of WEIRD participants. What does this stand for?
White, Educated, Industrialized, Rich, and Democratic.
(This sampling bias limits generalizability and is a major issue across most areas of psychological science.)
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While heritability estimates used to be limited to within-family comparisons, ______-based methods permit the analysis of genetic influences in large samples of unrelated individuals.
DNA
(These methods are particularly helpful for understanding genetically based developmental disabilities, which are often sufficiently rare that studies of unrelated individuals are necessary.)
151
True or False?
When the root cause of a disorder is a single gene, that one gene is responsible for all manifestations of the disorder.
False.
The gene starts a cascade of events, turning on and off multiple genes with effects on many different aspects of development.
152
True or False?
In some cases, a single gene can have both harmful and beneficial effects.
True.
Sickle- cell disease is a painful recessive-gene disorder affecting individuals who are homozygous for this trait (inheriting two sickle-cell genes, one from each parent). Individuals who are heterozygous for this trait (carrying one normal and one sickle-cell gene) have some abnormality in their blood cells but usually experience no negative effects. Yet the presence of sickle cell in an individual’s blood confers resistance to malaria, a benefit for those who live in regions of the world where malaria is common, like West Africa.
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Some single-gene conditions are carried on the X chromosome and are much more common in genetic males. What are a few examples of sec-linked disorders?
Minor: Male-pattern baldness and red– green colour blindness.
Serious: hemophilia and Duchenne muscular dystrophy.
Another sex-linked disorder is fragile-X syndrome, which involves mutations in the X chromosome and is the most common inherited form of intellectual disability.
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What are genome-wide association studies (GWAS)?
They are methods used in attempts to link multiple DNA segments (single-nucleotide polymorphisms, SNPs) with particular traits.
(For example, one recent study involving almost 80,000 adults identified 18 different genomic regions (mostly those expressed in brain tissue) implicated in individual differences in intelligence)
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What is genome-wide complex trait analysis (GCTA)?
A method that takes advantage of actual genetic resemblance across large groups of individuals, making it possible to tease apart aspects of genes and environment that are confounded within families.
(For instance, socioeconomic status (SES) is difficult to integrate into traditional measures of heritability because it is shared by twins within families. One study used GCTA to determine whether the effects of family SES on school achievement are genetically mediated by using a large representative sample of unrelated British schoolchildren.)
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In some cases, quantitative genetics and molecular genetics render divergent estimates of genetic contributions to individual differences. For example, GWAS and GCTA studies of traits such as reading ability suggest lower heritability than classic twin studies. Why might this be the case?
This puzzle of “missing heritability” suggests either that
1) the twin studies overestimated heritability or
2) that the molecular genetics studies underestimate it.
Notably, the molecular genetics studies have vastly larger sample sizes than the twin studies. They also include more diverse participants by virtue of their larger sample sizes.
Finally, twins may be particularly unrepresentative because, as discussed in Chapter 2, rates of twin births have increased due to the use of reproductive technologies like IVF, which are far more available to WEIRD families than to the rest of the globe.
156
What are neurons?
Cells that are specialized for sending and receiving messages between the brain and all parts of the body, as well as within the brain itself.
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What are the 3 components of a 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 toward 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.
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What are synapses?
Microscopic junctions between the axon terminal of one neuron and the dendritic branches or cell body of another.
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What are glial cells
Cells in the brain that provide a variety of critical supportive functions.
(Ie: the formation of a myelin sheath, 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.)
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Define myelin sheath.
A fatty sheath that forms around certain axons in the body and increases the speed and efficiency of information transmission.
161
What is the cerebral cortex?
The “gray matter” of the brain, consisting of four distinct lobes. It constitutes 80% of the human brain.
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The cerebral cortex includes 4 lobes. List the 4 lobes and briefly describe their main functions.
1) Occipital Lobe - major area of the cortex that is primarily involved in processing visual information
2) Temporal Lobe - major area of the cortex that is associated with speech and language, music, and emotional information
3) Parietal lobe - major area of the cortex that is associated with spatial processing and sensory information integration
4) Frontal Lobe - major area of the cortex that is associated with working memory and cognitive control. (The brains "executive").
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What are association areas in the brain?
Parts of the brain that lie between the major sensory and motor areas and that process and integrate input from those areas.
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Note - I did not create any flashcards about brain imaging techniques listed in the textbook. This may or may not be important to study?
165
What are cerebral hemispheres?
the two halves of the cortex
166
What is the corpus callosum?
A dense tract of nerve fibres that enable the two hemispheres of the brain to communicate.
167
What is cerebral lateralization?
The specialization of the hemispheres of the brain for different modes of processing
168
Define arborization.
formation of new dendritic trees and branches
169
What are spines in neurons?
formations on the dendrites of neurons that increase the dendrites’ capacity to form connections with other neurons.
170
Define myelination.
the formation of myelin (a fatty sheath) around the axons of neurons that speeds and increases information-processing abilities
171
What is synaptogenesis?
The process by which neurons form synapses with other neurons, resulting in trillions of connections.
172
The explosive generation of neurons and synapses during synaptogenesis results in many more neural connections than any one brain can use. This overabundance of synapses includes an excess of connections between different parts of the brain. Approximately 40% of this great synaptic superfluity is eliminated through what process?
synaptic pruning,
173
True or False?
The outer layers of the cortex shrink at a faster rate during adolescence than during either childhood or early adulthood
True.
The brain undergoes waves of synaptogenesis and synaptic pruning in the first months and years of life, but the brain also undergoes substantial changes during adolescence. The last area of the cortex to mature is the dorsolateral prefrontal cortex, which is vital for regulating attention, controlling impulses, foreseeing consequences, setting priorities, and other executive functions. It does not reach adult dimensions until after the age of 20, and synaptic pruning continues until individuals are in their 30s.
174
What Canadian psychologist is considered the father of neuropsychology?
Donald O. Hebb.
(Hebb’s groundbreaking work more than 70 years ago continues to guide our understanding of neural networks today.)
175
True or False?
The more often a synapse is activated, the stronger the connection between the neurons involved.
True.
Experience plays a central role in what is essentially a case of “use it or lose it.” Neurons that fire together wire together.
(Conversely, when a synapse is rarely active, it is likely to disappear: the axon of one neuron withdraws and the dendritic spine of the other is pruned away.)
176
What is the difference between experience-expectant plasticity and experience-dependent plasticity?
Experience-expectant plasticity 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—such as growing up in Canada or in the Amazon rain forest, experiencing frequent cuddling or abuse, and so on.
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The benefit of experience-expectant plasticity is that, because experience helps shape the brain, fewer genes need to be dedicated to normal development. That is, less information needs to be pre- installed in the brain. The downside is heightened _____________.
Vulnerability.
(If for some reason the experience that the developing brain “expects” does not occur, due to inadequate stimulation or impaired sensory receptors, development may be compromised. This phenomenon is exemplified by the classic work of Hubel & Wiesel, who deprived kittens of light exposure in one of their eyes. When the eye was later reopened, it was functionally blind; the cells that would have normally responded to it reorganized, responding instead to the eye that had continued to receive visual input.)
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What is an example of Cross-modal reorganization?
Individuals with early cataracts (or who are born blind) experience auditory takeover of brain areas that are typically part of the visual system, whereas individuals who are born deaf experience visual takeover of brain areas that are typically part of the auditory system.
Reiterating the concept of experience-expectant plasticity, areas of the brain that typically specialize in auditory or visual information behave in an experience-expectant manner. Absent the experiences that are species-typical (visual and/or auditory input), the brain reorganizes.
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