Chapter 4: Genetics, Evolution, Development, Plasticity Flashcards
genes
units of heredity that maintain their structural identity from one generation to another.
chromosomes
strands of genes
DNA
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
RNA
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
enzymes
biological catalysts that regulate chemical reactions in the body
homozygous
If you have the same genes on your two copies of some chromosome, you are homozygous for that gene
heterozygous
If you have an unmatched pair of genes, you are heterozygous for that gene
dominant gene
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
recessive gene
shows its effects only in the homozygous condition
ex. blue eye gene
sex-linked genes
genes on the sex chromosomes (designated X and Y in mammals)
autosomal genes
genes of all other chromosomes that are not sex-lined genes
sex-limited genes
on an autosomal chromosome, but
activated in one sex more than the other.
mutation
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
epigenetics
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
heritability
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.
monozygotic & dizygotic twins
identical (same genes) and fraternal (not the same genes)
phenylketonuria (PKU)
genetic inability to metabolize the amino acid phenylalanine
trait with high heritability can be modified by environ- mental interventions.
evolution
a change over generations in the frequencies of various genes in a population
artificial selection
choose individuals with a desired trait and make them the parents of the next generation
Lamarckian evolution
Lamarck’s theory of evolution through the inheritance of acquired characteristics
Using or failing to use some body structure does not change the genes
fitness
evolution improves fitness, which is operationally defined as the number of copies of one’s genes that endure in later generations
evolutionary psychology
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
altruistic behavior
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
kin selection
selection for a gene that benefits the individual’s relatives
reciprocal altruism
idea that individuals help those who will return the favor
group selection
According to this idea, altruistic groups thrive better than less cooperative ones
proliferation
production of new cells
stem cells
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.
migrate
Early in development, the primitive cells, not yet identifiable as neurons or glia, begin to migrate (move)
differentiates
As a cell differentiates into a neuron, it begins to form its dendrites, axon, and synapses
synaptogenesis
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
myelination
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
nerve growth factor (NGF)
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.
apoptosis
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
neurotrophin
Nerve growth factor is a neurotrophin, meaning a chemical that promotes the survival and activity of neurons.
fetal alcohol syndrome
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
far transfer
idea is to teach something challenging and hope students get smarter in other ways, too
focal hand dystonia
condition, known as “musician’s cramp”
closed head injury
sharp blow to the head that does not puncture the brain
stroke
common cause of brain damage, especially in older people, is temporary interruption of normal blood flow to a brain area
ischemia
more common type of stroke, result of a blood clot or other obstruction in an artery.
hemorrhage
less common type of stroke, result of a ruptured artery
edema
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
tissue plasminogen activator (tPA)
drug that breaks up blood clots
diaschisis
refers to the decreased activity of surviving neurons after damage to other neurons.
collateral sprouts
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
denervation supersensitivity
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
phantom limb
a continuing sensation of an amputated body part
deafferented
limb is deafferented because it has lost its afferent (sensory) input
