Genetics and Evolution of Behavior Flashcards
Gregor Mendel
demonstrated that inheritance occurs through genes
genes
units of heredity that maintain their structural identity from one generation to another
chromosomes
strands of genes (arranged in pairs) that also come in pairs
deoxyribonucleic acid (DNA)
a gene has been defined as part of a chromosome composed of the double-stranded molecule DNA
BUT, many genes do not have the discrete locations
sometimes several genes overlap on a stretch of chromosome. Sometimes a genetic outcome depends on parts of two or more chromosomes. In many cases, part of a chromosome alters the expression of another part without coding for any protein of its own.
ribonucleic acid (RNA)
A strand of DNA serves as a template (model) for the syn- thesis of ribonucleic acid (RNA) molecules, a single-strand chemical
messenger RNA
serves as a template for the synthesis of protein molecules.
four “bases” of DNA
adenine, guanine, cytosine, and thymine
their order determines the order of the corresponding bases along an RNA molecule
four “bases” of RNA
adenine, guanine, cytosine, and uracil.
he order of bases along an RNA mole- cule in turn determines the order of amino acids that compose a protein.
role of proteins
Some proteins form part of the structure of the body.
Others serve as enzymes, biological catalysts that regulate chemical reactions in the body.
Not all RNA molecules code for proteins.
Many RNA molecules perform regulatory functions.
homozygous
description for a particular gene for when you have the same genes on your two copies of some chromosome
heterozygous
have an unmatched pair of genes
eg, might have a gene for blue eyes on one chromosome and a gene for brown eyes on the other
dominant gene
shows a strong effect in either the homozy- gous or heterozygous condition
recessive gene
shows its effects only in the homozygous condition
Complications to Two Gene Determination
at least 10 genes that contribute to variations in eye color
At least 180 genes contribute to differences in people’s height
changes in the environment can increase or decrease the expression of a gene
Sample of Regular Chromosome Differences
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sex-linked genes
A gene on either the X or Y chromosome
genes on the sex chromosomes (designated X and Y in mammals)
usually mean X-linked genes
Y chromosome is small, with relatively few genes of its own, but it also has sites that influence the functioning of genes on other chromosomes
autosomal genes
All other chromosomes are autosomal chromosomes, and their genes are known as autosomal genes, as opposed to sex-linked genes
red-green color vision deficiency visual
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sex-limited genes
present in both sexes but active mainly in one sex
genes that control the amount of chest hair in men, breast size in women, amount of crowing in roosters, and rate of egg production in hens.
Both sexes have the genes, but sex hormones activate them in one sex and not the other, or one sex much more than the other. Many sex-limited genes show their effects at puberty.
mutation
a heri- table change in a DNA molecule.
Changing just one base in DNA to any of the other three types means that the mutant gene will code for a protein with a different amino acid at one location in the molecule
duplication or deletion
During the process of reproduction, part of a chromosome that ordinarily appears once might instead appear twice or not at all
microduplication or microdeletion
when duplication or deletion happens to just a tiny portion of a chromosome
Microduplications and microdeletions of brain-relevant genes are responsible for several psychological or neurological disorders, probably including some cases of schizophrenia
epigenetics
deals with changes in gene expression
all cells have the same DNA (except red blood cells which have no DAN)
but they get different genes turned on or off based on a number of factors
epigenetic changes can be inheritied for a limited amount of generations
histones and process of epigenetic change
proteins that bind DNA into a shape that is more like string wound around a ball
histone molecules in the ball have loose ends to which certain chemical groups can attach
To activate a gene, the DNA must partially unwind from the histones
environmental factor changes the histone causing it to loosen or tighten grip on DNA facilitating change
methyl group turns genes off
acetylg roup loosens histone’s grip and increases gene activation
heritability
if the variations in some characteristic depend largely on genetic differences, they are heritable
it is a range
determining heritability
compare monozygotic and dizygotic twins
study adopted children
identify specific genes linked to some behavior
candidate gene approach
researchers test a hypothesis, such as “a gene that increases the activity of the serotonin transporter may be linked to an increased risk of depression.”
has identified one gene with a significant influence on the risk of alcohol abuse, and a few other genes with moderate effects, but many studies have yielded small or uncertain effects
genome wide association study
examines all the genes while comparing two groups, such as people with and without schizophrenia
likely heritability from twin/adoption studies
loneliness, neuroticism, television watching, social attitudes, cognitive performance, educational attainment, speed of learning a second language
Environmental Modification
heritable does not mean unmodifiable
eg: phenylketonuria, or PKU, a genetic inability to metabolize the amino acid phenylalanine; diet can change it
Evolution
change over generations in the frequencies of various genes in a population
Lamarckian evolution
if you exercise your arm muscles, your children will be born with bigger arm muscles, and if you fail to use your little toes, your children’s little toes will be smaller than yours
largely disproven
fitness
operationally defined as the number of copies of one’s genes that endure in later generations
Evolutionary psychology
evolutionary and functional explanations— that is, how our genes reflect those of our ancestors and why natural selection might have favored the genes that pro- mote 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.
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
altruistic groups thrive better than less cooperative ones
alleles
pairs of genese that are aligned along chromosomes
weight of the brain
At birth, the human brain weighs approximately 350 grams
By the first year, the brain weighs approximately 1000 grams
The adult brain weighs 1200-1400 grams
development of neurons
the following processes:
Proliferation
Migration
Differentiation
Myelination
Synaptogenesis
new neurons later in life
– Stem cells: undifferentiated cells found in the interior of the brain that generate “daughter cells” that can transform into glia or neurons
– New olfactory receptors also continually replace dying ones
– The hippocampus and basal ganglia
▪ Replace almost 2% neurons in hippocampus per year
▪ The newn eurons are invariably small interneurons, not neurons with long axons extending to other brain areas
Brain in Adolescence
Synaptic density reaches adult levels at age 18
Immature connections between the limbic system, prefrontal cortex, and amygdala might produce “risky” behavior.
Increased activity in brain areas that anticipate reward likely why they are more risky
Adult Brain
fully mature at age 25; weight of brain starts to decrease at age 45
behavioral recovery after damage to brain
Mechanism:
– Increased brain stimulation
– Regrowth of axons
– Axon sprouting
– Denervation supersensivity
– Reorganized functional areas
denervation supersensitivity or receptor supersen- sitivity
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
helps compensate for de- creased input. However, when either collateral sprouting or denervation supersensitivity occurs, it can strengthen not only the desirable connections, but also undesirable ones, such as those responsible for pain
