🧠behav 2

The evolution of behavior

- "descent with modification" = emphasizing the idea of changes w/o necessarily implying improvement.

What are the main types of evidence to estimate the heritability of some behavior?

- 1) similarity bw monozygotic twins/dizygotic twins - 2) resemblance bw adopted children & their biological parents - 3) demonstration that a particular gene is more common than average among people who show a particular behavior

How does an epigenetic change differ from a mutation?

- A mutation is a permanent change in part of a chromosome. - An epigenetic change is an increase or decrease in the activity of a gene or group of genes

Suppose someone determines the heritability of IQ scores for a given population. Then society changes in a way that provides the best possible opportunity for everyone within that population. Will heritability of IQ increase, decrease, or stay the same?

- Heritability will increase bc heritability will estimate how much of the variation is due to differences in environment cannot account for much of the remaining differences in IQ scores. so the relative role of genetic differences will be greater

1 year old

- a huge amount of brain development occurs by the time a person is 1 year old

How does a sex-linked gene differ from a sex-limited gene?

- a sex linked gene is on the X or Y chromosome. A sex-limited gene is on an autosomal chromosome, but activated in one sex more than the other

DNA

- a strand of DNA serves as a template (model) for the synthesis of ribonucleic acid (RNA) -RNA = a single-strand chemical

Environmental Modification

- a trait with high heritability CAN be modified by environmental interventions - phenylketonuria (fee nil keet uhn your ee uh)/ PKU = a genetic inability to metabolize the amino acid phenylalanine - if PKU is not treated = phenylalanine accumulates to toxic levels this impairs brain development and leaves child mentally retarded, restless, and irritable. about 1 percent of Europeans carry a recessive gene for PKU. less asians, almost no Africans have the gene -PKU is a hereditary condition - even though PKU is a hereditary condition environmental interventions can modify it. Doctors in many countries they routinely test the levels of phenylalanine or its metabolites in each babies blood or urine. If the babies have high levels = indicating PKU. The doctors advise the parents to put the baby on a very strict low - phenylalanine diet to protect the brain. - success of this diet = indicates that heritable does not mean unmodified.

Autosomal genes

- all other chromosomes are known as autosomal genes

Heritability

- any estimate of the heritability of a trait is specific to a given population - example alcohol use: this has moderate heritability in the United States. So imagine a population somewhere where families teach VERY strict prohibitions on alcohol use maybe for religious reasons compared to other families that are more permissive. You have strong environmental differences, the genetic influences exert much less effect heritability will be relatively low. - another population where all families have the same rules, however people happen to differ in genes that affect their reactions to alcohol. In this population, heritability will be higher. - basically any estimate of heritability applies only to a particular population at a particular time. - third (3) the third and possibly the most decisive approach identify specific genes linked to some behavior. (candidate gene approach researchers test hypothesis, such as " a gene that increases the activity of the serotonin transporter may be linked to an increase risk of depression") -candidate gene approach has identified 1 gene with significant influence on the risk of alcohol abuse, few other genes with moderate effects, however many studies have yielded small/uncertain effects -another approach, a genome wide association study: this approach studies all the genes while comparing 2 groups, such as people w and w/o schizophrenia. Problem w this approach = it tests thousands of hypotheses at once ( one for each gene ) so there is a risk of seeing an apparent effect by accident, especially in studies with a small sample. Example: some disorder psychological/otherwise is more common in one ethnic group than another. Then any other gene that is common in that ethnic group will appear to be a "risk factor" then if that gene has nothing to do w/ the disorder -

sex-limited genes

- apart from the Sex linked genes are the sex limited genes -present in both sex but active mainly in one sex -examples: 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 - so both sexes will have this gene however, sex hormones activate them in one sex and not the other OR... one sex much more than the other - a lot of the sex limited genes will she their effects during puberty of that specific individual

Evolution

- change over generations in the frequencies of various genes in a population - we create 2 questions about evolution 1) how did some species evolve? 2) how do species evolve - how a species evolve = basically asking what it evolved from: ex humans are more similar to chimpanzees than to other species, biologist infer a common ancestor. - fossils also help to illuminate change over time. - when new evidence becomes available biologists change their pov/opinions about the evolutionary relationship be one species and another - contrast: the question: how species do evolve = basically asking how the process works & that process is a necessary outcome from what we know about reproduction. The reasoning goes as follows 1) bc genetic influences offspring resemble parents 2) mutations/recombinations/microduplications of genes = introduce new heritable variations which either help or harm an individual's chance of surviving and reproducing. 3) certain individuals will reproduce more than others & pass on their genes to the next generation so current generation of any species resemble the hoes who reproduced in the past. Change in the environment causes a different gene to increase the probability of survival and reproduction the gene will spread in the popumation

Heredity and Environment

- does singing ability depend on heredity or environment? = this question is meaningless you need both so let's change the question to... - Do the observed differences among individuals depend more on differences in heredity or differences in environment? example: if you sing better than someone else: reason could be different genes better training, or both.

Epigenetic changes in humans

- drug 💊 addiction produces epigenetic changes in the brain - the experience of feeling socially isolated or rejected alters the activity of hundred of genes - how well one of your grandparents was nourished or malnourished during their childhood correlates with your chances for a long, healthy life: why? bc apparently because of changes in your father's sperm cells

Sex-Linked gene

- example of a sex linked gene controls red-green color visions deficiency - any man with the recessive form of this gene on his X chromosome is red-green color deficient bc he has no other X chromosome - a women is color deficient only if she has that recessive gene on both of her X chromosomes for example 8% of human X chromosomes contain the gene for color vision deficiency then 8% of men will be color deficient, but less than one percent of women will be (0.08x0.08)

Female Mammal vs Male Mammal

- female mammals have 2 X chromosomes - male mammals have X and Y - during reproduction the female contributes an X chromosome and the male contributes either an X or a Y if the male contributes an X the offspring will be female if he contributes a Y the offspring will be male ( yes there are expectations to this rule but uncommon )

Experience modify gene expression

- first look at how gene expression is regulated, see how environmental factors can influence that regulation -proteins called histones hold 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 gene, DNA needs to unwind from the histones - the result of an experience maternal deprivation, cocaine exposure new learning some ways alters the chemical environment within a cell - in some cases the outcome adds acetyl groups (COCH3) to the histone tails near a gene causing the histones to loosen their grip on the DNA thus facilitating the expression of that gene - removal of the acetyl groups causes the histones to tighten their grip on the DNA, and turns the gene off. - another possibility is to add or remove methyl groups from DNA this usually happens at the promo for regions at the beginning of the gene. Adding methyl groups (CH3) to promoter turns off a gene, and removing them turns on the gene - example: traumatic experienced in early childhood decrease methylation of many brain genes this increasing the later risk of depression, post traumatic stress disorder etc.... - what you do at any moment doesn't only affect you but also produces epigenetic effects that alter gene expression for longer periods. - the distinction between genetic effects and experiential effects has become blurrier than ever. Experiences act by altering the activity of genes

Genes

- genes can be 1) dominant gene 2) recessive gene 3) intermediate gene

Sex linked genes

- genes on the sex chromosomes (designated X and Y in mammals) = known as sex-linked genes - biologist will speak of sex linked genes they usually mean X linked genes - Y chromosome is small with relatively few genes on it's own but the Y chromosome also has sites that influence the functioning of genes on other chromosomes

Lamarchian Evolution

- idea that the features we hardly use decreases over time: bc u hardly use your little toe it gets smaller and smaller in each succeeding generation - idea that if you exercise your arm muscles your children will be born w bigger arm muscles if ylh fail to use your little toe your children's little toes will be smaller than yours - biologist found no mechanism for lamarckian evolution to occur and no evidence that it does - using/not using body structures does not change genes - people w little toes will shrink in the furture only if the hoes w genes for smaller little toes happen to reproduce more than those with other sizes - people think humans have stopped evolving = bc modern medicine is keeping people alive welfare programs in countries give necessities of life for almost everyone so some people think that humans are no longer subjected to "survival of the fittest" - flaw in this = is evolution depends on reproduction NOT just survival of the fittest if a people with certain genes have more than the average number of children = their genes will spread in the population - evolution improves fitness: the number of copies of ones genes that endure in later generations. You have more kids than avg they survive long enough to where they are capable to reproduce = you are evolutionary fit whether or not you are successful in another way - you increase your fitness by supporting your relatives: who you share many of your genes and spread them by their own reproduction any gene which spread this = fit - genes that may increase fitness at one time and place might be disadvantageous after a change in the environment ex: the colorful tail feathers of the male peacock = enable to attract females but this may be harmful in thr presence of a new predator which responds to bright colors basically the genes of this current generation evolved because they were fit for previous generations these genes may/may not be adaptive in the future - does evolution benefit individuals or the species? Neither benefits the genes. You don't use your genes to reproduce yourself. Your genes use you to reproduce themselves

Heritability

- if variations in some characteristics depend mainly on genetic differences the characteristic has high heritability - scale of heritability: heritability ranges from 0 meaning no genetic contribution to the variation to 1 indicating complete control.

's anatomy is plastic

- instructions: put these axons here and those dendrites there & wait to see what happens - keep the connections that work the best and discard the others - continue making new connections and keep only successful ones These means the brain's anatomy is plastic The brain changes rapidly in early development and continues changing throughout life

Epigenetics

- just like mutations there is another cause for permanent changes in genes = epigenetics -epigenetics = deals w changes in gene expression: all the cells in your body has the same DNA as every other cell all but your red blood cells. Red blood cells have no DNA but the activity of your gene can vary - genes that are most active in your brain are not the same as those active in your lungs or kidneys maybe -those active in one part of your brain are not the most active in another part of your brain -many of the genes that are essential to developing fetus become less active birth all while the genes that where not essential for the fetus becomes important after birth -at puberty, certain genes that had been almost silent become much more active - a gene may be active in one person and not another after all monozygotic ("identical") twins sometimes differ in handedness, mental health, or other aspects - many experiences can turn a gene on or off. Forming a new memory or habit increases the activity of certain genes in particular neurons - if a mother rat is malnourished during pregnancy her offspring alter the expression of certain genes to conserve energy and adjust to a world in which food will presumably be hard to find if rich foods becomes abundant later in life those offspring's that are predisposed become of their gene expression, to a high probability of obesity and heart disease -epigenetic changes can be inherited: for at least a generation or two - when mice were conditioned to fear a particular odor the first and second generations of offspring showed increased sensitivity to that odor - when male mice were exposed to chronic stressful experiences, their offspring showed a weakened hormonal response to stresses and altered gene expression in part of the brain: the effect was traced to RNA molecules in the father's sperm

What example illustrates the point that even if some characteristic is highly heritable, a change in the environment can alter it?

- keeping a child w the PKU gene on a strict low phenylalanine diet prevents the mental retardation that the gene ordinarily causes. The general point is that sometimes a highly heritable condition can be modified environmentally

Behavioral Genetics

- nearly everything in psychology has significant heritability, but even so researchers cannot locate a gene with a strong link to behavior question: what are they over looking? - in addition to the possibility huge numbers of genes each exerting small effects, another possibility is microduplications or micro deletions -we talked before that micro duplications/microdeletions contribute to some cases. - another possibility = mutations that have a large effect but occur too rarely for typical research methods to find them. - another possibility is that what appear to be genetic effects might actually be epigenetic effects

How genes influence behavior

- no gene can produce its effect by itself - the gene will produce a protein that interacts with the rest of the body chemistry and w the environment. - how this gene will influence behavior = is a complex issue it's got many answers in different cases - a gene can influence your behavior even w/o being expressed in your brain. Example your genes make you unusually attractive. So as a result strangers smile at you and many people want to get to know you. -if their reactions to your appearance influences your personality then the genes altered your behavior by altering your environment. Example: picture a child born w genes promoting greater than average height/running speed. Bc of these factors the child shows early success at basketball and soon will spend more and more time playing basketball. Results the child will spend less than average time on other pursuits aka (watching tv, playing chess, or anything else). This illustrates the point: genes can influence behavior in round about ways.

Information (notes) on PKU

- required diet us difficult - people cannt eat eggs, dairy products, grains, and especially aspartame -aspartame = 50% phenylalanine - instead they eat an expensive formula containing the other amino acids - doctors long believed that children w PKU could quit the diet after a few years - experience later on demonstrated that high phenylalanine levels damage mature brains, too. A woman with PKU should be especially careful during her pregnancy and when nursing. - even a genetically normal baby cannot handle the enormous amounts of phenylalanine that an affected mother might pass through the placenta

how can we figure out the heritability of a characteristic?

- researchers use 3 kinds of evidence 1) first (1): they compare monozygotic (from one egg) twins and dizygotic (from two eggs) twins. people call Monozygotic twins = identical twins but this term differs in important ways example: some may be mirror images of each other: one right handed the other left handed but they still have the same genes. Dizygotic twins do not - stronger resemblance bw monozygotic than dizygotic twins suggest a genetic contribution. But evidence by itself is not totally decisive bc the way you look influences the way people treat you and so the way you act - researchers may examine/study virtual twins (children of the same age, adopted at the same time into a single family) grow up in the same environment from infancy but without any genetic similarity. Similarities in behavior imply environmental influences. But behavioral differences imply generic influences. -second (2): evidence from studies of adopted children. Any tendency for adopted children to resemble their biological parents imply a hereditary influence but this evidence is not always decisive - biological mother contributes not only her own genes but also the prenatal environment: the moms health, diet, smoking/drinking habits during her pregnancy will/can largely influence her child's development especially the brain development. so similarity between adopted child and the genetic mother could reflect either the genetic influences or the prenatal environment. - by using twin and adoption studies researchers have found: evidence for significant heritability of almost every behavior they have tested: this includes loneliness, neuroticism, TV watching, childhood misbehavior, social attitudes, cognitive performance, educational attainment, and speed of learning a second language. - roughly about the only behavior that has not shown a significant heritability is religious affiliation example: Protestant or Catholic

Dominate Gene

- shows a strong effect in either the homozygous or heterozygous condition

Translating information from DNA through RNA into proteins

- some proteins form part of the structure of the body -others serve as enzymes, biological catalysts that regulate chemical rxns in the body -not all RNA molecules code for proteins -Many RNA molecules perform regulatory functions

Genetic changes

- ways a gene can change 1) mutation = this is a heritable change in a DNA molecule. Changing one base in DNA to any of the other 3 types of means that the mutant gene will code for a protein w/ a different amino acid at one location in the molecule - mutations is not really a good thing it's "rarely advantageous" however those rare exceptions are important - we got the human FOXP2 gene differs from the chimpanzee version of that gene in just two bases however those two mutations modified the human brain and vocal apparatus in several ways which facilitate language development - another kind of mutation is a duplication or deletion: during the process of reproduction, part of a chromosome which normally (ordinarily) appears once (1) might instead appear twice (2) or not at all if this process happens to just a tiny portion of a chromosome we call it a microduplication or microdeletion - it is possible to for microduplication to be helpful most are not - microduplication and micro deletions of the brain - relevant genes be responsible for several psychological or neurological disorders, probably including some cases of schizophernia

DNA

-DNA contains four bases 1) adenine 2) guanine 3) cytosine 4) thymine - order of those bases determines the order of corresponding bases along an RNA molecule 1) adenine 2) guanine 3) cytosine 4) uracil -order of bases along an RNA molecule determines the order of Amino Acids that compose a protein example: if 3 RNA bases are in the order cytosine, adenine, and guanine then the protein adds the amino acid glutamine. If the next 3 RNA bases are uracil, guanine, and guanine, the next amino acid on the protein is tryptophan

Protein

-any protein consists of some combination of 30 amino acids in an order that depends on the order of DNA and RNA bases -we consider this a simple code compared to the complexity of body structures and functions that results from it

Genes

-bc of the many gene contributions to differences in phenotypes we express most of our genes in certain cells and not others -changes in our environment can increase or decrease the expression of a gene -genetic influences are more complex compared to what we once imagined

Mendelian Genetics

-before Gregor Mendel scientists thought that inheritance was a blending process where properties of the sperm and the egg simply mixed like 2 colors of paint -Mendel showed inheritance occurs through genes (units of heredity)

Heterozygous for PTC tasting gene

-each mate has 1 high taste sensitivity gene (T) both parents readily taste PTC (heterozygous dominate for PTC tasting) -but even though they dominate they are heterozygous so each parent transmits either a high taste sensitivity gene (T) or a low sensitivity gene (t) to any child/offspring -so therefore a child in this family will have a 25% chance of 2 (TT) genes, a 50% chance of heterozygous (Tt), 25% chance of (tt) -this example can be misleading bc it implies that a single gene produces a single outcome -even for eye color this is not true researchers have identified at least 10 genes contributing to variations in eye color -at least 180 genes contribute to variations in height

Phenylthiocarbamide (PTC)

-gene for high sensitivity to the taste of Phenylthiocarbamide (PTC) is dominant -gene for low sensitivity is recessive -only someone with two recessive genes has trouble tasting it

Genes

-genes come in pairs bc they are aligned along chromosomes (strands of genes) which also come in pairs -expedition to this rule = male mammal has unpaired X and Y chromosomes with different genes -classically = genes have been defined as part of a chromosome made up of double stranded molecule: deoxyribonucleic acid (DNA) -BUT many genes don't have the discrete locations we once thought they did -many times several genes overlap on a stretch of chromosome. -many times genetic outcome depends on parts of 2 or more chromosomes. -many times part of a chromosome alters the expression of another part w/o coding for any protein of its own

Heterozygous

-having an unmatched pair of genes you are heterozygous for that gene -example: you may have a gene for blue eyes on one chromosome and a gene for brown eyes on the other

Homozygous

-having the same genes on your two copies of some chromosome -you are homozygous for that gene

RNA

-messenger RNA = one type of RNA molecule: this serves as w template (model) for the synthesis of protein molecules.

Recessive Gene

-shows it's effects only in the homozygous condition -for example a gene for brown eyes is dominant and a gene for blue eyes is recessive -if you have 1 gene for brown eyes and 1 gene for blue eyes the result is brown eyes

main steps: translating information from DNA through RNA into proteins

1) DNA - self replicating molecule each base determines one base of the RNA 2) RNA - copy of one strand of the DNA a triplet of bases determines one amino acid. 3) Protein - some proteins become part of the body's structure. Others are enzymes that control the rate of chemicals rxns How DNA controls development of the organism? - The sequence of bases along a strand of DNA determines the order of bases along a strand of RNA; RNA in turn controls the sequence of amino acids in a protein molecule.

Punnett Square

A chart that shows all the possible combinations of alleles that can result from a genetic cross Tt x Tt

How does adding a methyl or acetyl group to a histone protein alter gene activity?

Adding a methyl group turns genes off. An acetyl group loosens histone's grip and increases gene activation

artificial selection

Breeding organisms with specific traits in order to produce offspring with identical traits. - Darwin says that nature also selects, if certain individuals are more successful than others their genes will become more popular in later generations.

Chapter 4

Genetics, Evolution, Development, and Plasticity