Module 2 Flashcards
(112 cards)
1
Q
Psychology/biopsychology has its historical roots in:
a) biology
b) chemistry
c) philosophy
d) psychology is a young science with no historical roots
A
c) philosophy
2
Q
Who established psychology as an academic discipline at Queen’s University?
a) Richard Beninger
b) Hans Dringenberg
c) Donald Hebb
d) George Humphrey
A
d) George Humphrey
3
Q
One of the fundamental differences between philosophy and psychology is the fact that…
a) only philosophy deals with the nature of human experience
b) only psychology attempts to understand consciousness in all species
c) only psychology has evolved into an empirical science
d) only philosophy has the answers to fundamental questions of human nature
A
c) only psychology has evolved into an empirical science
4
Q
Rats are able to discriminate…
a) their own behavioural state
b) walking from grooming
c) rearing from grooming
d) all of the above
A
d) all of the above
5
Q
What is Cross-modal plasticity?
A
Cross-modal plasticity refers to a re-arrangement of the functional organization of the brain, particularly the arrangements of different sensory areas of the neocortex.
(This type of re-arrangement is often observed in humans who lack one sensory modality from birth or early postnatal life, such as congenitally (that is, present at birth) blind or deaf individuals.)
6
Q
Cross-modal brain plasticity refers to:
a) the ability of the brain to recovery from brain damage
b) shifts in the functional organization of the brain between sensory modalities
c) shifts in the functional organization of the brain within one sensory modality
d) the disappearance of an anatomical brain area that is not used
A
b) shifts in the functional organization of the brain between sensory modalities
7
Q
Applying stimulation to the occipital lobe/visual cortex during Braille reading will:
a) interfere with reading performance
b) enhance reading performance
c) improve visual perception
d) cause participants to learn Braille at a faster rate
A
a) interfere with reading performance
7
Q
Neurons in area MT are responsive to:
a) touch
b) emotional face expressions
c) visual motion
d) tone sequences
A
c) visual motion
8
Q
Brain plasticity:
a) is greater in young brains
b) is limited to a period of early postnatal life
c) increases over the life-span
d) is observed only in brains deprived of sensory input
A
a) is greater in young brains
9
Q
You know how to define cross- modal brain plasticity. How would you define intra-modal plasticity?
a) the enlargement of a brain area that is deprived of input
b) shifts in the functional organization of the brain within a sensory modality
c) it is the same as cross-modal plasticity
d) none of the above are an appropriate definition
A
b) shifts in the functional organization of the brain within a sensory modality
10
Q
Imagine you lose one finger of your hand due to an accident. What might happen to the brain representation of that finger?
a) neurons representing the lost finger will die off
b) neurons representing the lost finger might become responsive to inputs from the remaining fingers
c) same as (b), but only in adult individuals
d). same as (b), but to a greater extent in young individuals
A
d) same as (b), but to a greater extent in young individuals
11
Q
What is DNA methylation?
A
A process where a methyl group becomes attached to DNA molecules and can change the expression of the affected gene without altering the DNA itself.
12
Q
True or False?
Epigenetics suggests traumatic events will not only change those who have experienced such events firsthand, but also their children and grandchildren.
A
True.
13
Q
Epigenetics refers to
a) changes in the genetic code (DNA)
b) changes in DNA transcription
c) changes in mRNA translation
d) inheritance mechanisms not directly related to the genetic code
A
d) inheritance mechanisms not directly related to the genetic code
14
Q
Dias and Ressler (2014) found that the offspring of mice that had learned to fear a specific odor:
a) do not respond to that odor
b) are more likely to approach that odor
c) show a startle response to that odor
d) avoid that odor
A
c) show a startle response to that odor
15
Q
The mechanism for this epigenetic effect (in the Dias & Ressler mice/odor study) was:
a) histone remodeling
b) increased DNA methylation
c) decreased DNA methylation
d) changes in DNA structure
A
c) decreased DNA methylation
16
Q
René Descartes advocated a philosophy (Cartesian dualism) that, in a sense, gave one part of the universe to science and the other part to the Church. He argued that the universe is composed of what two elements?
A
(1) physical matter, which behaves according to the laws of nature and is thus a suitable object of scientific investigation—the human body, including the brain, was assumed to be entirely physical, and so were nonhuman animals; and
(2) the human mind (soul, self, or spirit), which lacks physical substance, controls human behavior, obeys no natural laws, and is thus the appropriate purview of the Church.
17
Q
Most of the early North American experimental psychologists were totally committed to the ________ side of the nature–nurture issue.
A
nurture (learning)
18
Q
Who is considered to be the father of behaviorism?
A
John B. Watson
19
Q
At the same time experimental psychology was taking root in North America, _________ (the study of animal behavior in the wild) was becoming the dominant approach to the study of behavior in Europe.
A
ethology
20
Q
European ethology, in contrast to North American experimental psychology, focused on the study of ________ behaviors.
A
instinctive
(behaviors that occur in all like members of a species, even when there seems to have been no opportunity for them to have been learned), and it emphasized the role of nature, or inherited factors, in behavioral development.
21
Q
There are two lines of evidence against physiological- or-psychological thinking (the assumption that some aspects of human psychological functioning are so complex that they could not possibly be the product of a physical brain). What are those 2 lines of evidence?
A
1) The first line is composed of the many demonstrations that even the most complex psychological changes (e.g., changes in self-awareness, memory, or emotion) can be produced by damage to, or stimulation of, parts of the brain.
2) The second line of evidence is composed of demonstrations that some nonhuman species, particularly primate species, possess some abilities (e.g., complex problem solving) that were once assumed to be purely psychological and thus purely human.
22
Q
What is asomatognosia? ,
A
A deficiency in the awareness of parts of one’s own body.
(Asomatognosia typically involves the left side of the body and usually results from damage to the right frontal and parietal lobes. The point here is that, although the changes in self-awareness displayed by the patient were very complex, they were clearly the result of brain damage: Indeed, the full range of human experience can be produced by manipulations of the brain.)
23
Q
What is widely regarded as one hallmark of the human mind?
A
Self-awareness.
(But G. G. Gallup’s research on self- awareness in chimpanzees shows that nonhumans, which are assumed by some people to have no mind, are capable of considerable psychological complexity—in this case, self-awareness. Although their brains are less complex than the brains of humans, some species are capable of high levels of psychological complexity)
24
Now, let’s look at a way of thinking about the biology of behavior that has been adopted by most biopsychologists. This model boils down to the single premise that all behavior is the product of interactions among what three factors?
(1) the organism’s genetic endowment, which is a product of its evolution;
(2) its experience; and
(3) its perception of the current situation.
(Review Figure 2.3 on p.49 in the textbook)
25
Modern biology began in 1859 with the publication of what book by Charles Darwin?
On the Origin of Species.
(In this monumental work, Darwin described his theory of evolution—the single most influential theory in the biological sciences. Darwin was not the first to suggest that species evolve (undergo systematic change) from preexisting species, but he was the first to amass a large body of supporting evidence and the first to suggest how evolution occurs.)
26
Darwin presented what three kinds of evidence to support his assertion that species evolve?
(1) He documented the evolution of fossil records through progressively more recent geological layers.
(2) He described striking structural similarities among living species (e.g., a human’s hand, a bird’s wing, and a cat’s paw), which suggested that they had evolved from common ancestors.
(3) He pointed to the major changes that had been brought about in domestic plants and animals by programs of selective breeding.
(However, the most convincing evidence of evolution comes from direct observations of rapid evolution in progress. For example, Grant (1991) observed evolution of the finches of the Galápagos Islands—a population studied by Darwin himself—after only a single season of drought.)
27
Darwin argued that evolution occurs
through natural selection. What is natural selection?
He pointed out that the members
of each species vary greatly in their structure, physiology, and behavior and that
the heritable traits associated with high
rates of survival and reproduction are
the most likely ones to be passed on to
future generations.
He argued that natural selection, when
repeated for generation after generation,
leads to the evolution of species that are better adapted to surviving and reproducing in their particular environmental niche.
28
Why is social dominance an important factor in evolution?
1) In many species, dominant males copulate more than nondominant males and thus are more effective in passing on their characteristics to future generations.
2) In some species, dominant
females are more likely to produce more
and healthier offspring.
29
Why are courtship displays an important factor in evolution?
Courtship displays are thought to promote the evolution of new species.
A species is a group of organisms reproductively isolated from other organisms; that is, the members of a species can produce fertile offspring only by mating with members of the same species.
A new species begins to branch off from an existing species when some barrier (either geographic or behavioral) discourages breeding between a subpopulation of the existing species and the remainder of the species. Once such a reproductive barrier forms, the subpopulation evolves independently of the remainder of the species until cross-fertilization becomes impossible.
Only the suitable exchange of displays between a courting couple will lead to reproduction.
30
Define conspecifics.
Members of the same species.
31
Describe the evolution of vertebrates.
Complex multicellular water-dwelling organisms first appeared on earth about 800 million years ago. About 250 million years later, the first chordates evolved (animals with dorsal nerve cords). Chordates
are 1 of the 40 or so large categories, or phyla, into which zoologists group animal species.
The first chordates with spinal bones to protect their dorsal nerve cords evolved about 25 million years later. The spinal bones are called vertebrae, and the chordates that possess them are called vertebrates.
The first vertebrates were primitive bony fishes.
32
Describe the evolution of amphibians.
About 410 million years ago, the first bony fishes started to venture out of the water.
Fishes that could survive on land for brief periods of time had two great advantages: They could escape from stagnant pools to nearby fresh water, and they could take advantage of terrestrial food sources.
The advantages of life on land were so great that, through the process of natural selection, the fins and gills of bony fishes transformed into legs and lungs, respectively, and so it was that the first amphibians evolved about 370 million years ago.
Amphibians (e.g., frogs, toads, and salamanders) in their larval form must live in the water; only adult amphibians can survive on land.
33
Describe the evolution of reptiles.
About 315 million years ago, reptiles (e.g., lizards, snakes, and turtles) evolved from a branch of amphibians. Reptiles were the first vertebrates to lay shell-covered eggs and to be covered by dry scales.
Both of these adaptations reduced the reliance of reptiles on watery habitats. A reptile does not have to spend the first stage of its life in the watery environment of a pond or lake; instead, it spends the first stage of its life in the watery environment of a shell-covered egg.
And once hatched, a reptile can live far from water because its dry scales greatly reduce water loss through its water-permeable skin.
34
Describe the evolution of mammals.
About 225 million years ago, during the height of the age of dinosaurs, a new class of vertebrates evolved from one line of small reptiles.
The females of this new class fed their young with secretions from special glands called mammary glands, and the members of the class are called mammals after these glands.
Eventually, mammals stopped laying eggs; instead, the females nurtured their young in the watery environment of their bodies until the young were mature enough to be born. (The duck-billed platypus is one surviving mammalian species that lays eggs.)
Today, most classification systems recognize about 26 different orders of mammals. The order to which we belong is the order primates. We humans—in our usual humble way— named our order using the Latin term primus, which means “first” or “foremost.”
Apes (gibbons, orangutans, gorillas, and chimpanzees) are thought to have evolved from a line of Old World monkeys. Like Old World monkeys, apes have long arms and grasping hind feet that are specialized for arboreal (treetop) travel, and they have opposable thumbs that are not long enough to be of much use for precise manipulation. Unlike Old World monkeys, though, apes have no tails and can walk upright for short distances. Chimpanzees are the closest living relatives of humans; almost 99 percent of genes are identical in the two species, however, the actual ape ancestor of humans is likely long extinct.
35
Today, what are the seven classes of vertebrates?
three classes of fishes, plus amphibians, reptiles, birds, and mammals.
36
Why have primates proven particularly difficult to categorize?
Primates have proven particularly difficult to categorize because there is no single characteristic possessed by all primates but no other animals. Still, most experts agree there are about 16 groups of primates.
37
Describe the evolution of humankind.
Primates of the same group that includes humans are known as hominins. Hominins include six sub-groups including Australopithecus and Homo. Based on the fossil record, Homo is thought to be composed of at least eight species; seven of which are now extinct.
Neanderthals (Homo Neanderthalensis are one of those extinct Homo species. And we humans (Homo Sapiens) are the only one still kicking around.
Many experts believe that the Australopithecines evolved about 4 million years ago in Africa from a line of apes (australo means “southern,” and pithecus means “ape”). Several species of Australopithecus are thought to have roamed the African plains for about 2 million years before becoming extinct. Australopithecines were only about 4 feet tall, and they had small brains, but analysis of their pelvis and leg bones indicates that their posture was upright. Any doubts about their upright posture were erased by the discovery of the fossilized footprints.
The first Homo species are thought to have evolved from one species of Australopithecus about 2 to 2.8 million years ago.
One distinctive feature of the early Homo species was the size of their brain cavity, larger than that of Australopithecus but smaller than that of modern humans. The early Homo species used fire and tools and coexisted in Africa with various species of Australopithecus for about a half-million years, until the australopithecines died out.
Early Homo species also lived outside of Africa for about 1.85 million years. Then, about 275,000 years ago, early Homo species were gradually replaced in the fossil record by modern humans (Homo sapiens).
Paradoxically, although the big three human attributes—large brain, upright posture, and free hands with an opposable thumb—have been evident for hundreds of thousands of years, most human accomplishments are of recent origin. Artistic products (e.g., wall paintings and carvings) did not appear until about 40,000 years ago, ranching and farming were not established until about 10,000 years ago, and writing was not used until about 7,500 years ago.
38
Why is it difficult to reconstruct the events of human evolution?
Because the evidence is so sparse. Only a few partial hominin fossils dating from the critical period have been discovered. However, three important hominin fossil discoveries have been particularly enlightening.
39
What 3 important hominin fossil discoveries have been particularly enlightening for understanding the events of human evolution?
1) An uncommonly complete fossil of a 3-year-old early Australopithecus girl in Ethiopia.
2) Fossils indicating that a population of tiny hominins inhabited the Indonesian island of Flores as recently as 18,000 years ago.
3) Several early Australopithecine fossils with combinations of human and nonhuman characteristics in a pit in South Africa.
40
Describe nine commonly misunderstood points about evolution.
1) Evolution does not proceed in a single line. Although it is common to think of an evolutionary ladder or scale, a far better metaphor for evolution is a dense bush.
2) We humans have little reason to claim evolutionary supremacy. We are the last surviving species of a group (i.e., hominins) that has existed for only a blip of evolutionary time.
3) Evolution does not always proceed slowly and gradually. Rapid evolutionary changes (i.e., in a few generations) can be triggered by sudden changes in the environment or by adaptive genetic mutations.
4) Few products of evolution have survived to the present day—only the tips of the branches of the evolutionary bush have survived. Fewer than 1 percent of all known species are still in existence.
5) Evolution does not progress to preordained perfection—evolution is a tinkerer, not an architect. Increases in adaptation occur through changes to existing programs of development; and, although the results are improvements in their particular environmental context, they are never perfect designs. (Ie: the fact that mammalian sperm do not develop effectively at body temperature led to the evolution of the scrotum— hardly a perfect solution to any design problem.)
6) Not all existing behaviors or structures are adaptive. Evolution often occurs through changes in developmental programs that lead to several related characteristics, only one of which might be adaptive— the incidental nonadaptive evolutionary by-products are called spandrels. (One example of a spandrel is the human belly button—it is a nonfunctional by-product of the umbilical cord. Also, behaviors or structures that were once adaptive might become nonadaptive, or even maladaptive, if the environment changes.)
7) Not all existing adaptive characteristics evolved to perform their current function. Some characteristics, called exaptations, evolved to serve one function and were later co-opted to serve another. For example, bird wings are exaptations—they are limbs that initially evolved for the purpose of walking.
8) Similarities among species do not necessarily mean that the species have common evolutionary origins. Structures that are similar because they have a common evolutionary origin are termed homologous; structures that are similar but do not have a common evolutionary origin are termed analogous. The similarities between analogous structures result from convergent evolution, the evolution in unrelated species of similar solutions to the same environmental demands. (ie: a bird’s wing and a human’s arm have a basic underlying commonality of skeletal structure that suggests a common ancestor; in contrast, a bird’s wing and a bee’s wing have few structural similarities, but they both evolved because of the common advantage of flight)
9) There is now considerable evidence that Homo sapiens mated with other Homo species (e.g., Neanderthals) they encountered. The discovery of this pattern of mating changes the way we should view our origins: We are not the product of a single ancestral Homo population; rather, we are the combined offspring of many Homo populations that once coexisted and interacted.
41
True or False?
Brain size and intellectual capacity are closely related.
False.
Although healthy adult human brains vary greatly in size—between about 1,000 and 2,000 grams—there is no clear relationship between overall human brain size and intelligence.
42
A more reasonable approach to the study of brain evolution has been to compare the evolution of different brain ________.
Regions.
(For example, it has been informative to consider the evolution of the brain stem separately from the evolution of the cerebrum (cerebral hemispheres). In general, the brain stem regulates reflex activities that are critical for survival (e.g., heart rate, respiration, and blood glucose level), whereas the cerebrum is involved in more complex adaptive processes such as learning, perception, and motivation.)
43
Comparing the brain stems and cerebrums of several species that are living descendants of species from which humans evolved draws what three important points about the evolution of the human brain?
1) The brain has increased in size during evolution.
2) Most of the increase in size has occurred in the cerebrum.
3) An increase in the number of convolutions—folds on the cerebral surface—has greatly increased the surface area of the cerebral cortex, the outermost layer of cerebral tissue.
44
Although the brains of related species differ, there are fundamental similarities such as:
All brains are constructed of many neurons, and the neural structures in the brains of one species can usually be found in the same locations in the brains of related species.
45
There has been a long-standing debate on whether humans and other animals inherit their behavioral responses or acquire them through learning. This is called the _______ debate.
Nature-nurture.
46
The condition that can result from damage to the right parietal lobe and typically involves a lack of awareness of one’s own body parts (most commonly on the left side) is known as _______.
Asomatognosia.
47
Darwin proposed that the striking similarities among living species were evidence that they shared a common _______.
ancestor
48
Through selective _______ programs, major changes have been made to domestic animals and plants.
breeding
49
In some species, the _______ male is likely to copulate
more and, therefore, pass on his genes to the future generations.
dominant
50
One distinctive feature of early Homo species was that they had brains _______ than Australopithecus but _______ than modern humans.
larger, smaller
51
Incidental nonadaptive evolutionary by-products such as the belly button are called _______.
spandrels
52
During the course of the vertebrate evolution, birds emerged approximately _______ years ago.
160 million
53
The overall human brain size does not predict _______.
intelligence
54
Over millions of years, there has been a remarkable
increase in the surface area of the _______, the outmost layer of the cerebral tissue in humans.
cerebral cortex
55
Evolutionary psychologists suggest that male–female
_______ during copulation ensures that the offspring will survive, reproduce, and pass on their genes to the next generation.
bonding
56
_______ structures are similar because of convergent evolution.
Analogous
57
What were the two key facts that Darwin did not understand, despite them being fundamental to his theory of evolution?
1) He did not understand why conspecifics differ from one another, and
2) he did not understand how anatomical, physiological, and behavioral characteristics are passed from parent to offspring.
(While Darwin puzzled over these questions, an unread manuscript in his files contained the answers. It had been sent to him by an unknown Augustinian monk, Gregor Mendel.)
58
Mendel studied inheritance of ________ in pea plants.
seed color (brown or white).
59
What are Dichotomous traits?
Occur in one form or the other, never in combination. For example, seed color is a dichotomous pea plant trait: Every pea plant has either brown seeds or white seeds.
60
What are True-breeding lines?
Breeding lines in which interbred members always produce offspring with the same trait (e.g., brown seeds), generation after generation.
61
What is the difference between a phenotype and a genotype?
An organism’s observable traits are referred to as its phenotype;
the traits that it can pass on to its offspring through its genetic material are referred to as its genotype.
62
What are alleles?
The two genes that control the same trait.
(Organisms that possess two identical alleles (e.g., two white-seed alleles) are said to be homozygous for that trait; those that possess different alleles (e.g., one white-seed allele and one black-seed allele) for a trait are said to be heterozygous for that trait.)
63
What are chromosomes?
The threadlike structures in the nucleus of each cell.
64
The process of cell division that produces gametes (egg cells and sperm cells) is called _______.
meiosis
65
What is a zygote?
A fertilized egg cell.
66
What is genetic recombination?
During the first stage of meiosis, the chromosomes line up in their pairs. Then, the members of each pair cross over one another at random points, break apart at the points of contact, and exchange sections.
67
In contrast to the meiotic creation of the gametes, all other cell division in the body occurs by ________.
mitosis.
68
Describe the structure of a DNA molecule.
Each chromosome is a double-stranded molecule of deoxyribonucleic acid (DNA). Each strand is a sequence of nucleotide bases attached to a chain of phosphate and deoxyribose; there are four nucleotide bases: adenine, thymine, guanine, and cytosine. It is the sequence of these bases on each chromosome that constitutes the genetic code—just as sequences of letters constitute the code of our language.
The two strands that compose each chromosome are coiled around each other and bonded together by the attraction of adenine for thymine and guanine for cytosine.
This specific bonding pattern has an important consequence: The two strands that compose each chromosome are exact complements of each other. For example, a sequence of ade- nine, guanine, thymine, cytosine, and guanine on one strand is always attached to a complementary sequence of thy- mine, cytosine, adenine, guanine, and cytosine on the other.
69
Describe the replication process of a DNA molecule.
Replication is a critical process of the DNA molecule. Without it, mitotic cell division would not be possible.
The two strands of DNA start to unwind. Then, the exposed nucleotide bases on each of the two strands attract their complementary bases, which are floating in the fluid of the nucleus. Thus, when the unwinding is complete, two double-stranded DNA molecules, both of which are identical to the original, have been created.
Chromosome replication does not always go according to plan; there may be errors. Sometimes, these errors can have significant clinical consequences. For example, in Down syndrome (an extra chromosome in each cell). But more commonly, errors in replication take the form of mutations—alterations of individual genes.
70
What is is the one exception to the rule that chromosomes always come in matched pairs (called autosomal chromosomes)?
The one exception is the pair of sex chromosomes--the pair of chromosomes that determines an individual's sex.
There are two types of sex chromosomes, X and Y, and the two look different and carry different genes. Females have two X chromosomes, and males have one X chromosome and one Y chromosome. Traits influenced by genes on the sex chromosomes are referred to as sex-linked traits.
71
True or False?
Virtually all sex-linked traits are controlled by genes on the X chromosome because the Y chromosome is small and carries few genes.
True.
72
Traits controlled by genes on the X chromosome occur more frequently in one sex than the other. Why?
If the trait is dominant, it occurs more frequently in females. Females have twice the chance of inheriting the dominant gene because they have twice the number of X chromosomes. In contrast, recessive sex-linked traits occur more frequently in males.
The reason is that recessive sex-linked traits are manifested only in females who possess two of the recessive genes—one on each of their X chromosomes—whereas the traits are manifested in all males who possess the gene because they have only one X chromosome. The classic example of a recessive sex-linked trait is color blindness. Because the color- blindness gene is quite rare, females almost never inherit two of them and thus almost never possess the disorder; in contrast, every male who possesses one color-blindness gene is color blind.
73
Structural genes contain the information necessary for the synthesis of proteins. What are proteins?
long chains of amino acids; they control the physiological activities of cells and are important components of cellular structure.
74
All the cells in the body (e.g., brain cells, hair cells, and bone cells) contain exactly the same genes. How then do different kinds of cells develop?
Part of the answer lies in those stretches of DNA that lack structural genes—indeed, although all genes were once assumed to be structural genes, those genes comprise only a small portion of each chromosome.
Although the stretches of DNA that lack structural genes are not well understood, it is clear that they include portions that do serve a function. These portions, called promoters, are stretches of DNA whose function is to determine whether or not particular structural genes are converted into proteins through a two-phase process known as gene expression.
75
Why is the control of gene expression by promoters is an important process?
It heavily influences how a cell will develop and how it will function once it reaches maturity.
(Promoters are like switches because they can be regulated in two ways: They can be turned up, or they can be turned down. Those proteins that bind to DNA and increase gene expression are called activators; whereas those that bind to DNA and decrease gene expression are called repressors.)
76
Gene expression involves what two phases?
1) Transcription - the small section of the chromosome that contains the gene unravels, and the unraveled section of one of the DNA strands serves as a template for the transcription of a short strand of ribonucleic acid (RNA). RNA is like DNA except that it contains the nucleotide base uracil instead of thymine and has a phosphate and ribose backbone instead of a phosphate and deoxyribose backbone. The strand of transcribed RNA is called messenger RNA because it carries the genetic code out of the nucleus of the cell. Once the messenger RNA leaves the nucleus, the second phase of gene expression expression begins:
2) Translation - the messenger RNA attaches itself to any one of the many ribosomes present in the cell’s cytoplasm (the clear fluid within the cell). The ribosome then moves along the strand of messenger RNA, translating the genetic code as it proceeds.
Each group of three consecutive nucleotide bases along the messenger RNA strand is called a codon. Each codon instructs the ribosome to add 1 of the 20 different kinds of amino acids to the protein it is constructing; for example, the sequence guanine-guanine-adenine instructs the ribo- some to add the amino acid glycine. Each kind of amino acid is carried to the ribosome by molecules of transfer RNA; as the ribosome reads a codon, it attracts a transfer RNA molecule that is attached to the appropriate amino acid. The ribosome reads codon after codon and adds amino acid after amino acid until it reaches a codon that tells it the protein is complete, whereupon the completed protein is released into the cytoplasm.
77
Flip to see a more brief explanation of the two phases of gene expression.
1) The first phase involves the transcription of the DNA base-sequence code to an RNA base-sequence code.
2) The second phase involves the translation of the RNA base- sequence code into a protein.
78
What was the purpose of the Human Genome Project?
To compile a map of the sequence of all 3 billion nucleotide bases that compose human chromosomes.
(It was motivated by potential medical applications.)
79
The Human Genome Project has changed our understanding of ourselves and revolutionized the field of genetics. What are 3 major contributions of this project?
1) Many new techniques for studying DNA were developed. Many things that were impossible before the project are now routine, and things that took months to accomplish are now possible in only a few hours. Using this new technology, genomes have already been established for many species, including those of many long-extinct species, leading to important insights into evolution.
2) The discovery that we humans, the most complex of all species, have relatively few structural genes surprised many scholars. Humans have about 21,000 structural genes; mice have about the same number, and corn has many more. Indeed, protein-encoding genes constitute only about 1 percent of human DNA. Researchers have now generated a nearly complete map of the entire set of proteins encoded for by our genes: the human proteome.
3) Many variations in the human genome related to particular diseases have been identified. However, this has proven to be less useful than anticipated: So many genes have been linked to each disease that it has proven difficult to sort out the interactions among the numerous genes and experience. Compounding the problem is that even when many genes have been linked to a disease, all of them together often account for only a small portion of its heritability.
80
Despite its relative youth, epigenetic research has already amassed an impressive array of discoveries. What are 5 important ones?
1) Epigenetic investigations of nongene DNA have identified many active areas. Many of these active areas seem to control the expression of nearby genes. Clearly, the belief that nongene DNA is junk DNA is no longer tenable
2) Many epigenetic mechanisms that can modulate gene expression have been discovered. Two of the most widely studied are DNA methylation and histone remodeling. Both of these can either decrease or increase expression.
3) So much interest has been generated by epigenetics research that a world-wide effort is now underway to catalogue the epigenome of each cell type. As of 2018, the epigenomes of over 600 cell types had been characterized.
4) Some epigenetic effects involve post-transcription alterations to RNA that do not affect the RNA base sequence. This occurs in all RNA molecules that have been examined to date, though special attention has been paid to epigenetic modifications of messenger RNA and transfer RNA. The high prevalence of these RNA modifications has led to a new effort: The cataloguing of the so-called epitranscriptomes of various cell types.
5) Remarkably, epigenetic mechanisms (e.g., DNA methylation, histone remodeling) can be induced by particular experiences (e.g., neural activity, hormonal state, changes to the environment) and can last a lifetime.
81
What is DNA methylation?
The reaction that occurs when a methyl group attaches to a DNA molecule, usually at cytosine sites in mammals.
82
What is Histone Remodeling?
The reaction that occurs when histones (proteins around which DNA is coiled) change their shape and in so doing influence the shape of the adjacent DNA— there are several different mechanisms by which this can occur.
83
What is an epigenome?
It represents a catalogue of all the modifications to DNA within a particular cell type other than changes to the nucleotide base sequence.
84
What is the epitranscriptome of a cell?
The epitranscriptome of a cell refers to all those modifications of RNA that occur after transcription—that do not involve modifications to the RNA base sequence.
85
What is the field of transgenerational epigenetics?
A subfield of epigenetics that examines the transmission of experiences via epigenetic mechanisms across generations.
(For example, it has been shown that when mice experience an odor associated with a painful shock, the memory of that experience is passed on to subsequent generations through epigenetic mechanisms. There is grow- ing evidence that inheritance via transgenerational epigenetic mechanisms can also occur in humans.)
86
According to Mendel’s experiments, the dominant trait will result in about _______ of the offsprings in the second generation.
three-quarters
87
An offspring’s observable traits are called its _______ while its genetic material is referred to as _______.
phenotype,
genotype
88
A single trait is controlled by two expressions of the same gene called _______.
alleles
89
Egg and sperm cells are also called _______, and each contains half the usual number of chromosomes.
gametes
90
During fertilization, the resulting _______ contains a full set of chromosomes.
zygote
91
The four nucleotide bases in DNA are adenine, thymine, cytosine, and _______.
guanine
92
Accidental errors in individual genes are called _______.
mutations
93
_______ are stretches of DNA that control the process
of gene expression.
Promoters
94
_______ mechanisms such as DNA methylation and
histone remodeling may control gene.
Epigenetic
95
The shape of DNA can be influenced by the change of
shape of the adjacent _______.
histones
96
All chromosomes except _______ chromosomes come
in matched pairs.
sex
97
The first phase of gene expression involves the
transcription of DNA to RNA, and the second phase involves the _______ of RNA base-sequence code into a sequence of amino acids.
translation
98
The Human Genome Project discovered that only _______ percent of human DNA contains protein-encoding genes.
1
99
What is ontogeny?
The development of individuals over their life span.
100
What is phylogeny?
The evolutionary development of species through the ages.
101
True or False?
The PKU gene is recessive.
True.
The pattern of transmission of PKU through the fam- ily trees of afflicted individuals indicates that it is transmitted by a single gene mutation. About 1 in 100 people of European descent carry the PKU gene; but because the gene is recessive, PKU develops only in homozygous individuals (those who inherit a PKU gene from both their mother and their father).
102
Briefly explain the biochemistry of phenylketonuria (PKU)?
PKU homozygotes lack phenylalanine hydroxylase, an enzyme required for the conversion of the amino acid phenylalanine to tyrosine. As a result, phenyl- alanine accumulates in the body; and levels of dopamine, a neurotransmitter normally synthesized from tyrosine, are particularly low. The consequence is abnormal brain development.
103
True or False?
The results of the Minnesota Study of Twins Reared Apart study found that In general, adult monozygotic twins were substantially more similar to one another on all psychological dimensions than were adult dizygotic twins, whether or not both twins of a pair were raised in the same family environment.
True.
104
True or false?
A heritability estimate is about individual development.
False.
It is not about individual development; it is a numerical estimate of the proportion of variability that occurred in a particular trait in a particular study as a result of the genetic variation in that study. Heritability estimates tell us about the contribution of genetic differences to phenotypic differences among the participants in a study; they have nothing to say about the relative contributions of genes and experience to the development of individuals.
105
True or False?
Heritability estimates tend to be about the same regardless of the particular trait or behavior under consideration and regardless of the particular basis used to calculate them.
True.
In the representative Western samples that have been studied, all complex traits and behaviors have substantial heritability estimates—most between 40 and 80 percent.
106
Why do several eminent geneticists to argue that no more heritability estimate studies should be conducted?
The discovery that genetic variability contributes substantially to individual differences in virtually all human traits and behaviors. What could more heritability estimate studies possibly add?
(These geneticists are, however, excited about the potential of two other types of twin studies that have been increasingly reported - twin studies of epigenetic effects and twin studies of the effects of experience on heritability.)
107
Why should the common practice of referring to monozygotic twins as identical twins should be curtailed?
Epigenetic differences. Fraga & colleagues They took tissue samples from 40 pairs of monozygotic twins, ranging in age from 3 to 74. Then, they screened the tissues for epigenetic alterations (e.g., DNA methylation, histone remodeling).
They found that the twins were epigenetically indistinguishable early in life, but differences between them accumulated as they aged, each type of tissue displaying a different epigenetic profile. As a result, the former assumption that monozygotic twins are genetically identical was disproven.
108
What are disease-discordant monozygotic twin studies?
This kind of study begins with the identification of monozygotic twins who are discordant for a disease of interest. Then one searches each pair for epigenetic differences focusing on those areas of DNA that are thought to be involved in the disorder.
109
What is One major implication of Turkheimer et al. study? (Who assessed heritability of intelligence in two samples of 7-year-old twins: those from families of low socioeconomic status (SES) and those from families of middle to high SES.)
It forces us to think about intelligence as developing from the interaction of genes and experience, not from one or the other. It seems that one can inherit the potential to be of superior intelligence, but this potential is rarely realized in a poverty-stricken environment.
Their study showed heritability estimates for intelligence in the middle- to high-SES twins was, as expected, about 70 percent. However, the heritability estimate for intelligence in the twins from low-SES families was only 10 percent. This effect was subsequently replicated and extended to other age groups: babies and adolescents.
110
Why have many politicians argued against special programs for the poor?
Because most heritability estimates of intelligence are high. They incorrectly argue that because intelligence is largely inherited (i.e., it has a high heritability estimate), special programs for the poor are a waste of money. However, the findings of Turkheimer and colleagues suggest otherwise: Reducing poverty would mean that all children would be able to reach their intellectual potential.
111
