Chapter 4: Genetics, Evolution, Development, Plasticity

Question 1

genes

Answer 1

units of heredity that maintain their structural identity from one generation to another.

Question 2

chromosomes

Answer 2

strands of genes

Question 3

DNA

Answer 3

gene has been defined as part of a chromosome composed of the double-stranded molecule

DNA contains four “bases”—adenine, guanine, cytosine, and thymine

order of those bases determines the order of corresponding bases along an RNA molecule—adenine, guanine, cytosine, and uracil

Question 4

RNA

Answer 4

a single-strand chemical

messenger RNA— serves as a template for the synthesis of protein molecules

order of bases (adenine, guanine, cytosine, and uracil) along an RNA molecule in turn determines the order of amino acids that compose a protein; any protein consists of some combo of 20 amino acids, in an order that depends on the order of DNA and RNA bases

not all RNA molecules code for proteins, many perform regulatory functions

Question 5

enzymes

Answer 5

biological catalysts that regulate chemical reactions in the body

Question 6

homozygous

Answer 6

If you have the same genes on your two copies of some chromosome, you are homozygous for that gene

Question 7

heterozygous

Answer 7

If you have an unmatched pair of genes, you are heterozygous for that gene

Question 8

dominant gene

Answer 8

shows a strong effect in either the homozygous or heterozygous condition

you express most of your genes in certain cells and not others, and changes in the environment can increase or decrease the expression of a gene

ex. brown eye gene

Question 9

recessive gene

Answer 9

shows its effects only in the homozygous condition

ex. blue eye gene

Question 10

sex-linked genes

Answer 10

genes on the sex chromosomes (designated X and Y in mammals)

Question 11

autosomal genes

Answer 11

genes of all other chromosomes that are not sex-lined genes

Question 12

sex-limited genes

Answer 12

on an autosomal chromosome, but
activated in one sex more than the other.

Question 13

mutation

Answer 13

a heritable change in a DNA molecule; rarely advantageous

duplication or deletion - During the process of reproduction, part of a chromosome that ordinarily appears once might instead appear twice or not at al

Question 14

epigenetics

Answer 14

changes in gene expression

Various experiences can turn a gene on or off; can be inherited, at least for a generation or two.

The result of an experience in some way alters the chemical environment within a cell, causing the histones (proteins) to loosen their grip on the DNA, and facilitating the expression of that gene

Question 15

heritability

Answer 15

If the variations in some characteristic depend largely on genetic differences, the characteristic has high heritability

ranges from zero, indicating no genetic contribution to the variation, to one, indicating complete control.

Question 16

monozygotic & dizygotic twins

Answer 16

identical (same genes) and fraternal (not the same genes)

Question 17

phenylketonuria (PKU)

Answer 17

genetic inability to metabolize the amino acid phenylalanine

trait with high heritability can be modified by environ- mental interventions.

Question 18

evolution

Answer 18

a change over generations in the frequencies of various genes in a population

Question 19

artificial selection

Answer 19

choose individuals with a desired trait and make them the parents of the next generation

Question 20

Lamarckian evolution

Answer 20

Lamarck’s theory of evolution through the inheritance of acquired characteristics

Using or failing to use some body structure does not change the genes

Question 21

fitness

Answer 21

evolution improves fitness, which is operationally defined as the number of copies of one’s genes that endure in later generations

Question 22

evolutionary psychology

Answer 22

concerns how behaviors evolved; how our genes reflect those of our ancestors and why natural selection might have favored the genes that promote certain behaviors

assumption is that any behavior characteristic of a species arose through natural selection and presumably provided some advantage, at least in ancestral times

Question 23

altruistic behavior

Answer 23

an action that benefits someone other than the actor

gene that encourages altruistic behavior would help other individuals survive and spread their genes, at a possible cost to the altruistic individual

common in humans

Question 24

kin selection

Answer 24

selection for a gene that benefits the individual’s relatives

Question 25

reciprocal altruism

Answer 25

idea that individuals help those who will return the favor

Question 26

group selection

Answer 26

According to this idea, altruistic groups thrive better than less cooperative ones

Question 27

proliferation

Answer 27

production of new cells

Question 28

stem cells

Answer 28

Early in development, the cells lining the ventricles of the brain divide. Some cells remain where they are as stem cells, continuing to divide, whereas others migrate to other parts of the nervous system.

Question 29

migrate

Answer 29

Early in development, the primitive cells, not yet identifiable as neurons or glia, begin to migrate (move)

Question 30

differentiates

Answer 30

As a cell differentiates into a neuron, it begins to form its dendrites, axon, and synapses

Question 31

synaptogenesis

Answer 31

the formation of synapses, begins long before birth, but it continues throughout life, as neurons form new synapses and discard old ones. The process generally slows in older people, as does the formation of new dendritic branches

Question 32

myelination

Answer 32

later and slower stage of neuronal development is myelination, the process by which glia produce the insulating fatty sheaths that accelerate transmission in many vertebrate axons

Myelin forms first in the spinal cord and then in the hindbrain, midbrain, and forebrain. Myelination continues gradually for decades and increases as a result of learning a new motor skill

Question 33

nerve growth factor (NGF)

Answer 33

Initially, the sympathetic nervous system forms far more neurons than it needs. When one of its neurons forms a synapse onto a muscle, that muscle delivers a protein called nerve growth factor (NGF) that promotes the survival and growth of the axon. An axon that does not receive NGF degenerates, and its cell body dies.

Question 34

apoptosis

Answer 34

If its axon does not make contact with an appropriate postsynaptic cell by a certain age, the neuron kills itself through a process called apoptosis, a programmed mechanism of cell death

Question 35

neurotrophin

Answer 35

Nerve growth factor is a neurotrophin, meaning a chemical that promotes the survival and activity of neurons.

Question 36

fetal alcohol syndrome

Answer 36

condition marked by hyperactivity, impulsiveness, difficulty maintaining attention, varying degrees of mental retardation, motor problems, heart defects, and facial abnormalities. Drinking during pregnancy leads to thinning of the cerebral cortex that persists to adulthood

Question 36

far transfer

Answer 36

idea is to teach something challenging and hope students get smarter in other ways, too

Question 37

focal hand dystonia

Answer 37

condition, known as “musician’s cramp”

Question 38

closed head injury

Answer 38

sharp blow to the head that does not puncture the brain

Question 39

stroke

Answer 39

common cause of brain damage, especially in older people, is temporary interruption of normal blood flow to a brain area

Question 40

ischemia

Answer 40

more common type of stroke, result of a blood clot or other obstruction in an artery.

Question 41

hemorrhage

Answer 41

less common type of stroke, result of a ruptured artery

Question 42

edema

Answer 42

Both ischemia and hemorrhage lead to many of the same problems, including edema (the accumulation of fluid), which increases pressure on the brain and the probability of additional strokes

Question 43

tissue plasminogen activator (tPA)

Answer 43

drug that breaks up blood clots

Question 44

diaschisis

Answer 44

refers to the decreased activity of surviving neurons after damage to other neurons.

Question 45

collateral sprouts

Answer 45

After a cell loses input from an axon, it secretes neurotrophins that induce other axons to form new branches, or collateral sprouts, that take over the vacant synapses

Question 46

denervation supersensitivity

Answer 46

if a certain set of synapses becomes inactive—perhaps because of damage elsewhere in the brain—the remaining synapses become more responsive, more easily stimulated. This process of enhanced response, known as denervation supersensitivity

Question 47

phantom limb

Answer 47

a continuing sensation of an amputated body part

Question 48

deafferented

Answer 48

limb is deafferented because it has lost its afferent (sensory) input