Genetics and Evolution Notes PDF

Task 1 Post Discussion What are the laws of Mendel? 1. Law of dominance: in heterozygous conditions, dominant allele is expressed 2. Law of segregation: each organism has 2 alleles per trait, these segregate during meiosis, and offspring inherits one from each parent 3. Law of independe...

Task 1 Post Discussion What are the laws of Mendel? 1. Law of dominance: in heterozygous conditions, dominant allele is expressed 2. Law of segregation: each organism has 2 alleles per trait, these segregate during meiosis, and offspring inherits one from each parent 3. Law of independent assortment: alleles are sorted independently and aren’t inherited together a. Only for alleles of different chromosomes Exceptions to the laws - Crossover can happen when linked - partial/incomplete dominance, codominance → normal distribution - Phenotypically different from Mendellian model but punnett squares still apply - X-linked alleles; men only inherit 1 (law of segregation) - Polyphenisms: organisms develop phenotypes based on environmental factors (law of dominance) - lethal gene: Mendel’s findings are based on equal survival - Quantitative traits: height involves more than 1 gene; additive effects - IQ, risk of mental disorders, cognitive abilities (e.g. memory, attention span) Examples of normal distribution - Blood pressure, skin pigmentation, weight How can we estimate heritability? - Twin studies: mono and dizygotic twins to study the relationship between nature and nurture in genetic expression - Nature: Mutations, changes in DNA - Hardy-Weinberg theorem: used to predict the frequency of an allele in a population - P & Q are alleles - Eye color is mostly inherited - A lot of variation in eye color: polygenic (multiple genes involved) - Nurture: environmental influences - Lifespan is 20-30% inherited (diet, lifestyle play bigger roles) - Broad-sense heritability: general measure of genetic influence but doesn’t distinguish between types of genetic variance 2 𝑉𝐺 𝑉𝐺 - 𝐻 = 𝑉𝑃 = 𝑉𝐺+𝑉𝐸 2 - A high 𝐻 value indicates high genetic variance and low phenotypic variance and vice versa - Low heritability: high 𝑉𝐸 value 2 - 𝐻 : heritability - 𝑉𝐺: genetic variance - Measured by calculating the number of alleles and how well they coordinate with a certain phenotype; if allelic and phenotypic variation match, this means that genes highly determine the trait, and the reverse means environment plays a larger impact - 𝑉𝑃: phenotypic variance - 𝑉𝐸: environmental conditions - Narrow-sense heritability: includes additive genetic variance and dominance effects How do Mendel’s laws apply to sex chromosomes? - Laws of segregation and independent assortment apply - Segregation occurs in anaphase - Independent assortment occurs during prophase  - Most do not share Mendellian pattern of inheritance due to men having a single X chromosome - X and Y are not homologous Explain Rett syndrome - Autosomal disease - Spontaneous mutation - Mostly in females - Random X-inactivation of cells affecting neurology; for males lacking a second X have all cells affected - Deactivation occurs in bands - Males typically die in childbirth or early on - Can survive do to some mutations not being as severe as others - Mosaicism: if the mutation occurs later in development, less parts of the body can be affected - Klinefelter (XXY) Task 2 Post-discussion 1. Top 1 has a silent/synonymous mutation Top 2 has a missense/nonsynonymous mutation Top 3 has a missense/nonsynonymous mutation Top 4 insertion + substitution, missense and nonsense mutation? Not sure but i got that frameshift mutation caused the 2 nonsense mutations 2. - Nucleic acid - Bases (A, T, C & G) bonded by hydrogen bonds - Antiparallel, complementary base pairs - Purines (A & G), 2 rings and pyrimidines (C & T), 1 ring - Locus is specific location on a chromosome for a certain gene 3. - Replication bubble + forks - Helicase breaks hydrogen bonds, so splits strands and single-strand proteins maintain this - Enzyme topoinz.. relieves fork from strain - Primases synthesize primers (pieces of RNA) that initiate the replication - Replication from 5 to 3 end - DNA- polymerase binds to primer - Leading and lagging strand (strand replicated in fragments (Ozaki), bc of the specific direction (only at 3 end of new strand nucleotides are added)) - Fragments of lagging strand are binded by DNA-ligase (makes phospho di ester bonds) - Bc of composition the strands they will automatically bind together after replication - Semiconservative mode of replication 4.  - Simple sequence repeat? 5. a. - DNA methylation: added methyl group to DNA that results in repression of gene expression (CPG islands) - histone modification: modification at histone tail -> unpacking -> more accessible  - RNA associated regulation: non-coding RNA pieces (transfer RNA, ribosomal RNA) interfere with mRNA 6. - He thinks that adaptation during someone’s life (so adapting to environment) can be passed to offspring, but is not possible (only a little bit in the sense of epigenetics) - Use and disuse theory, means that when people for example had a tail that this would disappear in their life if it wasn't used (also impossible bc has disappeared over generations) - Eggs of fetus (female) are already there when fetus in mother, so 2 generations can get affected by epigenetics 7. - Correlation between low-birth weight and increase of disease (obesity + cardiovascular), bc low-birth weight results in ‘energy-saving’ genes? Task 3 Population genetics 1. What is the HW-theorem? + assumptions =mathematical tool to estimate p2 + 2pq + q2 = 1 (p + q = 1) p= dominant allele q= recessive allele The Hardy–Weinberg principle relies on a number of assumptions: (1) random mating (population structure is absent and matings occur in proportion to genotype frequencies), (2) the absence of natural selection, (3) a very large population size (i.e., genetic drift is negligible), (4) no gene flow or migration, (5) no mutation, and (6) the locus is autosomal. You can use it when the frequencies of the alleles are known to predict what the genotype frequencies should be in the next generation. Alternatively, we can use genotype frequencies to calculate allele frequencies whenever the genotype frequencies are known. To do this, we multiply the frequency with which the genotype occurs in the population by the number of copies of the allele carried by each genotype. 2. What is natural selection? - Other types of selection + few examples Natural selection occurs when individuals with certain genotypes are more likely than individuals with other genotypes to survive and reproduce, and thus to pass on their alleles to the next generation. Darwin: - Struggle is not random totally based on phenotype - It will move a population eventually towards a type of phenotype Directional selection - one of the 2 phenopytes is more adapted (example: trees covered in soot → darker moths) Stabilizing selection - Selection favors individuals with a treat near the population mean (example: intermediate fish length most optimal) (bottle neck) Disruptive selection - The extremes are favored Balancing selection - Balancing selection refers to any kind of selection that preserves polymorphism, that is, keeps alleles from drifting to low frequencies and being lost by chance. (example: When the heterozygotes for the alleles under consideration have a higher fitness than the homozygote: sickle cell and malaria) 3. Absolute- vs relative fitness Fitness: The success of an organism to survive ILL finish these learning goals sections when I get home! :)) 4. Explain Tay-sach and CF disease - Why are they relatively common? Cystic fibrosis, for example, is a genetic disorder in which the lungs build up with fluid, leading to pneumonia. The median life expectancy for Americans with cystic fibrosis is 37 years. The disease is caused by mutations to the CFTR gene, which encodes a chloride channel in epithelial cells. 5. Explain mutation-selection equilibrium Once a new mutation arrives, drift and selection may begin to act on it. If the allele is deleterious, selection will act to reduce its frequency. But other new mutations at the same locus will keep emerging, lifting up the allele’s frequency. → The production of new alleles and negative selection will act like opposing teams in a tug-of-war. Together, this mutation selection balance will result in an equilibrium frequency of any new allele. - Mutation selection balance helps explain why rare deleterious alleles with recessive effects persist in populations, adding to genetic variation. - Usual mutations: deleterious or normal, very rare that mutations result in advantages. (only in an environment where you check them. In another environment the mutations could have the opposite effect.) Task 4: How did lifeforms increase in complexity? 1. How did life start? → different hypotheses - RNA world hypothesis - Environmental conditions are unclear - RNA formed the following molecules - Can store and perform function - Needed for DNA and proteins - Replicator and can replicate - RNA can do that - Primordial Soup - Organic molecules formed spontaneously in Earth’s early oceans - Panspermia - Life did not begin here but was brought here by comets - Metabolism first hypothesis - Some form of modern metabolism existed before the first macromolecules - Metabolic fossils fed up from 2. What was the benefit of endosymbiosis? - Mitochondria: They get safety, food source - the provide - Chloroplasts: allow photosynthesis - get safety and food source-> secondary endosymbiosis - Endosymbiosis: prokaryotes consumed oxygen, entered the single cell host, the relationship from paracytic to neutralists(?) changed, now they cannot live on their own - The DNA of mitochondria looks more similar to bacterial DNA than human, they have a double membrane - Mitochondria came first because every eukaryotic cell has a mitochondria, only some eukaryotic cells have a chloroplast → prove that this was the order - Benefit in having a endosymbiosis: more efficient because it extract more ATP from each glucose molecule than glycolysis 3. Prokaryotes vs Eukaryotes Eukaryotes have a nucleus, have more organelles Prokaryotes have circular, free floating DNA, eukaryotes have linear, concentrated DNA 4.. What is a genomic conflict? - Arises when various genomic elements don’t align, having conflicting interests in terms of their replication and transmission to the offspring, so when one is contained in another (such as mitochondria in eukaryotic cells) - When inheritance is a-symmetrical -> eukaryotic cells - Types: - Intragenomic: jumping-genes -> copy genes into new locations? - not in the interest of the whole organism but part - B-chromosomes/meiotic drive genes: - Mitochondrial DNA vs eukaryotic DNA 5. How was the genomic conflict on endosymbiosis solved? (Nucleus & Mitochondria) - Shared function - Minimization of the mitochondrial genome - Gene transfer to the nucleus - Mitophagy - “eating the mitochondria” - Host cell bound division of the reproduction of the mitochondria to its own - Uniparental inheritance of Mitochondria → no need to compete - (if this would not happen, it can harm the main organelle - similar to cancer - not being aligned with the - Every cell having the same DNA but shutting off different parts - 6. How come different cells in a multicellular organism do not look and function alike? - Every cell have the same DNA but different genes are expressed, the others are “turned off” - Cooperation: groups of cells become dependent on each other, being so specialized, not being able to live alone → if cells stop working, the whole organism stops working 7. How do darwinians’ principles of evolution apply to cancer? - Natural selection → survival of the fittest cells regarding their environmental conditions - Genetic Variation → mutation create variation among cancer cells - Competition → between healthy cells and cancer cells - Adaptation → the population of cancer cells adapt - Faster replication - Evasion of the immune system - Being more resistant and aggressive - Not an entire organism evolves but a population in the body evolves - Disregulaiton of genes, which allowed the creation of cancer - due to unicellular and multicellular gene expression - Atavism/atavistic theory of cancer - cancerous cells may revert to a more primitive, ancestral state during tumor development → cancer representing a kind of evolutionary “reversal” - Warburg effect: tumors prefer glycolysis to generate energy, since its faster but less efficient - To fight: immune system, checking for DNA damage, tumor suppressing gene, force cells to go into apoptosis - Due to a lot of environmental factors that can be damaging, there is a lot of cellular exchange, to get rid of possible damaged cells  - Muscle , epithelial, connective, nervous tissues → due to different levels of exchange ratio, these cells also have different values but also different mutation levels Task 5: Speciation and Phylogenetic Trees 1. How does speciation occur? Speciation is the process by which new species form. It occurs when groups in a species become reproductively isolated and diverge. a. What is a species? Darwin claims it’s « impossible » to define a species because of the theory of evolution, everything is descending from a common ancestor. A group of individuals or organisms that can reproduce with one another in nature and produce fertile offspring. A population may become subdivided into two populations that no longer exchange genes, making it possible for them to diverge into two separate species. 2. Does speciation have to be caused by an isolating barrier? -Geographic isolation is a common way for the process of speciation to begin: rivers change course, mountains rise, continents drift, organisms migrate, and what was once a continuous population is divided into two or more smaller populations. (Allopatric speciation.) -In a situation in which a population extends over a broad geographic range and mating throughout the population is not random. Individuals at one extremity would have zero chances of mating with individuals on the other extremity. (Peripatric speciation.) -Prezygotic barriers: keep organisms of different species from mating with each other and forming hybrid species. -Postzygotic barrier: occurs after fertilization and results in reduced zygote viability or offspring with lower fitness.  3. What is the difference between microevolution and macroevolution? -Microevolution refers to small-scale changes within a species or population. These changes occur over shorter timescales (within a few generations) and involve alterations in allele frequencies due to mechanisms like mutation, natural selection, genetic drift, and gene flow. -Macroevolution refers to large-scale evolutionary changes that leads to the emergence of new species, families or taxonomic groups. It happens Over much longer time scales and involves the accumulation of microevolutionary changes that eventually result in significant biological differences. In essence, Microevolution deals with changes within a species. Macroevolution involves changes that result in the formation of new species or larger taxonomic groups. 4. How is a phylogenetic tree organized? (different terms: node, base node, branch) -Internal node: any node that has child nodes. -Tip: corresponds to individual organism, species, or to sets of species, as long as each tip makes up a separate branch on the tree. -Monophyletic: group of organisms that make up a clade. -Polyphyletic: taxonomic group that doesn't form a clade. -Paraphyletic: descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups.  5. Compare and contrast gradual change and punctuated equilibrium theory. -Punctuated equilibrium: species remain relatively unchanged for long periods (equilibrium), interrupted by rapid significant change (punctuation). Changes occur in small, isolated populations, which then spread to the other populations. -Gradual Change: evolutionary changes occur slowly and steadily over long periods. Continuous accumulation of small changes within species, leading to the formation of new species over time. 6. What are phylogenetic trees based on? What is the data that leads to a specific tree? -Fossils: bone structure. -DNA based: how much common DNA there is between two species. -Characteristics, that are « scored »: In a survey of insects, for example, wings might be present or absent in each species. Horns on a group of antelope species might be scored as either curved or straight. Task 6 1. What is reciprocal selection? - Reciprocal selection: selection that occurs in 2+ species due to mutual interactions. Coevolution’s prerequisite. - Examples: - gophers and tics, bacteria attacked by bacteriophages but bacteria develop defense mechanism - Wasps and fruit fly: flies do not thrive in food-scarce environments when they have the encapsulating trait (northern europe) = weaker reciprocal selection. Flies adapt more to the wasp parasite when the food is abundant - Also affected by genetic drift, the prevalence of wasps in the area. Differs over time and space. a. How do trade offs emerge? - Pine trees and strength of pine cones: birds try to eat pine cones → making pine cones thicker but energy costly and doesn't protect from squirrels. Evolution find balance between all factors. - Snake and newts: if newts develop stronger toxins, snake evolves higher toxin resistance, but snake will have reduced speed  - If both traits escalate = evolutionary arms race (but is still limited by fitness, see below) - Trade-off worthwhile if general fitness is positive. - Competition within host - Virulence: how much damage parasite can do to host (best virus is an undetectable one to the host) - Increase in virulence: outcompete other parasites to harm the host in order to survive. If virulence is too high, the hist will die. - Decrease in virulence: avoid host’s death in order to promote virulence in other hosts (increased proliferation) 2. What is coevolution? - Coevolution: process of reciprocal evolutionary change between species, driven by natural selection - Big process of evolution bc all species cohabitate and thus influence each other. - Adaptation = 2 requirements - Ecological interactions in species - Reciprocal selection - Geographic mosaic theory: - Geographic variation (3 types): - Type selection - Strength selection - Distribution of traits that evolve in response to selection - Example: invasive species modified by humans - Usually antagonists or mutualistic. - Antagonists: negative dependent frequency selection on each other (species) - Mutualistic selection: generate positive frequency dependent selection on each other (species) 3. What is frequency-dependent selection? - Frequency-dependent selection: fitness depends on frequency: how common or rare phenotype is within population - Negative: rare phenotypes have fitness advantage bc rare, if become more common advantage decreases - Parasites adapt to most common host, most adapted multiply and fitness of common hosts decreases. Rare/uncommon host phenotypes increase → become common and most common parasite decreases and rarer phenotypes in parasites increases - Constantly shifting frequency on both host and parasite = antagonistic coevolution - Positive: common phenotype has advantage, but advantage decreases if they become rarer - Mimicry (Müllerian) 4. What are the forms of symbiosis? - Mutualism: both species benefit from relationship (bees and flowers: flowers are pollinated by bees and bees get nectar) - Vulnerability: If very dependent on coevolved partner, and partner goes extinct, other species might also go extinct. - Not mutualism, but certain butterflies only mate on specific plant. If this plant goes extinct, there’s a good chance the butterfly will become extinct as well. - Commensalism: one species benefits and other species does not really benefit/suffers no loss of fitness (shark protects fish but fish doesn’t harm shark) - Parasitism: one species benefits while harming another, host and parasite (tics on mammals) - Parasite has limited effects on host, typically smaller than host - Negative positive relationship : predator-prey relationship, deceptive pollination: no nectar provided in exchange for pollination) - Exploitation: a. What is endosymbiosis ? 5. What is Batesian and Müllerian mimicry? - Müllerian mimicry: harmful species resemble each other to ward off predators. - Wasps and bees resemble each other and both possess venom, but have different costs (wasp can sting indefinitely while bees will die with a single sting) - Batesian mimicry: harmless species (cheaters) resemble harmful species. Protection from predators. But toxic species should evolve away from mimicked trait to avoid being hunted by predator. Cheaters will always try tot catch up to the toxic species. = coevolutionary chase - Hoverfly and wasp a. What is introgression? - Introgression: the movement of alleles from one species or population to another. - Rapid convergence of shared coloured patterns - Adaptive radiation: species diversify into new species from ancestral species - New patterns moved through hybridizing species - // : Former parent species and new species hybridize: bring out beneficial traits (wild and domesticated species to induce disease resistance, occurs naturally and through human intervention) - Other example: humans and neanderthal genes - Summary: - Cross-breeding between species can sometimes give viable fertile hybrids, and traits can over time end up in other species. Quite rare, but under right selective pressures, can happen. Complicates comparison of genome between both species (seem more closely related than they actually are) 6. How do pathogens adapt to their hosts? - Pathogen does not want to kill host. - Pathogen multiplies very quickly → selection occurs very quickly - HIV can produce a billion offspring in a day. - Emergence of many COVID variants (waves) - Some viruses don't have any gene that inhibits mutations - Higher probability of evolving advantage = way of survival (antigenic drift) - Example: different flu virus mutation, reason why you have the flu every year  - Bacteria increasing harmfulness - Tuberculosis: benin before entering lungs - Form of virulence - Retrovirus: RNA virus that uses an enzyme called reverse transcriptase to become part of the host cell’s DNA. - The virus that causes AIDS, the human immunodeficiency virus (HIV), is a type of retrovirus. - Many genes have viral origin. - What may seem like a disease, certain traits may give advantages. There are limits, evolution is tinkering: finding immediate solutions for immediate problems that in the long run may solve a bigger issue. Task 7 PS: How did sexual reproduction evolve and lead to sexual selection? 1. Compare and contrast mitosis and meiosis. 2. How did sexual reproduction emerge? (pros and cons) 3. How did asexual reproduction emerge? (pros and cons)  4. How does sexual selection work? 5. What are the selective pressures within and between the sexes? 6. What is parthenogenesis? a. Explain the fly example 7. What are the advantages and disadvantages of sexual reproduction? Task 8 1. What is inclusive fitness theory? An individual's fitness: direct fitness: an individual's own reproductive fitness Indirect fitness: reproductive fitness of other individuals who share the same alleles An individual's benefit of helping another individual increases with increased relatedness which might lead to altruistic behavior if the benefits outweigh the costs. According to Hamilton's rule, kin selection causes genes to increase in frequency when the genetic relatedness of a recipient to an actor multiplied by the benefit to the recipient is greater than the reproductive cost to the actor. Reciprocity: conditional help/support Kin selection: unconditional help/support 2. How can we use game theory to explain social behavior? Modeling interactions between animals within one species or across species can given a clue to predict future behavior. Some strategies become dominant but there are also “games” with oscillating “dominant” strategies due to the interconnected nature of different strategies (e.g. rock > scissors > paper > rock ) 3. Explain the presence of dominant strategies A dominant strategy always provides the highest pay-off regardless of another player's behavior and strategy. Lizard example: yellow > orange > blue > yellow ⇒ frequency dependant selection 4. How did altruism evolve? Living in groups is beneficial and altruism is a fair price to pay for these benefits. It can improve and reinforce learned behaviors. Human society reinforces altruism through norms and values. Raising the offspring of other members of the species can increase one's social standing in the group. Mutualism: direct benefit Altruism: delayed benefit or maybe no benefit at all. (time delay!) Does true altruism exist? Kinship influences altruistic behavior. You might expect some benefit later on when acting altruistic towards less related individuals. Living in groups can have many benefits and trade-offs but it is usually more beneficial to live in groups. 5. How and why does kinship influence behavior? Worker bees do not reproduce themselves because they are more related to their sisters than to their own theoretical offspring (r=0.75 vs r=0.50)  Could also explain the unusual closeness of monozygotic twins. Kin-selection works by detection of phenotypical relatedness markers or by living in close proximity to each other. 6. How can we calculate genetic relatedness for individuals? Probability that two individuals share the same allele due to inheritance from a common ancestor (coefficient of relatedness (r)) 7. How does direct and indirect reciprocity relate to kinship? Direct reciprocity involves individuals helping others with the expectation that the favor will be returned in the future, fostering cooperation among non-kin. Indirect reciprocity occurs when individuals help others based on their reputation, leading to reciprocal altruism even in large, unrelated groups. Kinship, however, typically drives cooperation based on shared genes (kin selection), while reciprocity mechanisms extend cooperation beyond kin relations. 8. What is the difference between proximate and ultimate studies on behavior? Proximate studies: - How does the behavior happen - Mechanism Ultimate studies: - Why does the behavior happen - Utility 9. Complete the exercises 1) Mother and child: r=0.5 or 50% Half brothers: r=0.25 or 25% Brothers: r=0.5 or 50%  2) Relatedness to brother: 0.5 so 2 brothers = 100% of your alleles Relatedness to cousin: 0.125 so 8 cousins = 100% of your alleles 3) Worker bee and drone: 0.25 or 25% Worker bee and worker bee: 0.75 or 75% Task 9 1) What are Parent-Offspring and Parent-Parent genetic conflicts a) Genetic offspring and parent conflicts. Offspring wishes to take as much nutrients as possible, while the parent wants to ensure it’s own survival b) Paternal Conflict theory: i) Mother wishes to limit available recourse for young, to ensure her own fitness. ii) Father wishes their offspring to take as much recourse available, to ensure their genetic transfer to next generation (1) What happens to mother is not relevant to fitness of the father c) Examples: i) IGF2 and IGF2R (1) IGF2, comes from the paternal genome, a hormone that allows nutrients to flow from parent to offspring. (2) IGF2R, Comes from maternal gene, inhibits IGF2 ability to allow nutrient flows to offspring 2) Haigs Theory a) Haigs Theory: Theorized that parent-parent conflict between M and F is due to uncertainty of paternal certainty for the males(unsure if it is their child) , making it  more advantageous for Males to have children that take as much resources as possible to ensure their long term fitness i) Example: Chicks in birds may exaggerate their hunger amounts, to get more resources from their mother. b) Balancing Mechanisms i) Mothers with placentas may have more mechanisms to control nutrient extraction compared to egg laying mothers ii) Quality and Quantity of offspring between species 3) Link to Placental Mammals a) Most imprinting genes are present in placental mammals, during fetal growth i) Less need to have genetic imprinting when a self sufficient / isolated egg b) Advantages to Placenta i) Placenta is more efficient at nutrient transfer, allowing for higher levels of development within young, especially with nervous system development c) Disadvantages i) There is an arms race between paternal and maternal genes which dictate the amount of nutrients given to the young d) Types of placental mammals i) Marsupials (1) Born at early stages of development but keep young in pouches ii) Eutherian mammals (1) Humans, significantly more complex (2) Internal Placenta, most extensive imprinting iii) Monotremes (1) Lay eggs, give birth early, least placental like. Least amount of imprinting in group 4) How is genetic conflict related to monogamy vs promiscuity ? a) Promiscuous dad with monogamous mom i) Paternal genes in promiscuous species tend to take more nutrients from mother for offspring, promoting the fathers fitness at the expense mother AND siblings (could be half siblings) b) Monogamous dad with promiscuous mom i) Maternal alleles promote less growth within young, c) Promiscuous genes overpower monogamous ones i) More competition 5) Epigenetic constructs a) Longterm, pre programmed, fundamental b) Modifications in gene expression do not change DNA. Due to environment i) Genomic Imprinting is one of these mechanisms (1) Different methylation patterns between sexes, (2) Different form standard epigenetics modifications bc they are long term and are programed, not responses c) Examples of development constructs :  i) X inactivation ii) Genomic Imprinting 6) What is the molecular solution to parental conflict a) Genomic imprinting b) Example i) IGF2 and IGF2R c) DMR (differentially methylated regions) i) Regions differently methylated on genome between sexes, Task 10 PS: How did human cognitive abilities evolve, and how do they differ from other animals? 1. How does brain size relate to cognitive ability? Brain enlarges over generations when more cognitive capacity is required Allometric line: brain size in relation to body mass ○ Humans lie above it ○ Allometry: the relationship between a body part and body size; proportional scaling Encephalization quotient; brain weight divided by weight predicted by allometric line ○ Better way to measure intelligence than just looking at size 2. How are the 5 clues related to human cognitive ability? Clue 1: energy expansiveness compared to cognitive ability of human brain ○ To increase brain size; increase energy input to brain, redistribute energy from other body parts Tool use; less muscle is required → trade-off dynamics ○ Diet change: meat consumption, fruit vs. leaves, cooking the food Higher nutrient consumption, sterilizing it Clue 2: tool use ○ Facilitated the trade-off of using more energy for cognitive functions (brain) and less for muscles) ○ Tool making & use itself requires more cognitive ability; planning, problem solving Clue 3: language & theory of mind ○ Machiavellian intelligence & social brain hypotheses: as group size increases, more cognitive power is required For maintaining/monitoring relationships: memory, manipulation, etc. Competition of group living Social exchange: interactions, reciprocal altruism, detecting cheats, etc. Benefits of group living Relative brain size increases when social network increases ○ Weaknesses of this theory: Cannot account for general, but specific cognitive abilities of mammals E.g. language  Leaves great shifts in brain size unexplained Animals that show a deviation ○ Cultural intelligence hypothesis: social part of brain grows larger, but there are other components of the brain that manage other things Animals that live in solitary groups may need to use other parts of their brain and that accounts for size deviations Other hypotheses do not account for general brain functions Social interaction requires IQ to have culture More general intelligence; pass on things that aren’t heritable (stories, books, etc.) 3. What is the ink between tool use and complex cognition in the animal kingdom? Tool use is an unusual trait ○ Likely independently evolved Used to obtain food, protection Capacity for innovation ○ New Caledonian Crows; make larva fishing hooks with a bendy piece of wire Throw unbreakable nuts on the street for cars to drive over/break them Why did they evolve tool use? No large brains Short beaks, weak skulls; same food source as other birds ○ Energy diverted from developing these natural benefits Care for their young for an unusually long time ○ Picture the goal & understand how the world around will react Why did tool use evolve? ○ Ecological intelligence hypothesis: finding food & processing food → greater cognitive abilities Fruit eaters vs. leaf eaters ○ Finding ways to outcompete members of group/same species ○ Tools can survive time in a group; sharing knowledge Larger brains of group animals also facilitate this 4. How do humans differ from their ape relatives? Less strong, larger brains 5. What are the current theories to explain the large brains? (Sociality) Proximate explanations ○ Changes in neural circuitry: frontal and temporal lobes are linked in primate brains by long-distance nerve fibers, humans & chimps evolved denser nerve fibers, with humans having the most ○ Gyrification of the brain; folding to increase surface area Expensive tissue hypothesis: not sociality, but diet that predicts brain size ○ Nutrient-rich diet; more calories → brain expansion ○ Cooking food ○ Fewer muscles (expensive); living in groups Cooperative breeding and alloparental care ARHGAP11B: ○ Only found in human & neanderthal brains ○ Increases number of neurons in neocortex (language), increases gyrification FoxP2 ○ Language SRGAP2 HAR1