Bio Final 3

• 1. Complexity of the genotype-phenotype relationship-no single factor is both necessary and sufficient to cause a phenotype, causes of variation of a phenotype does not equal cause of a phenotype
• 2. Confoundment of frequency and apparent causation in complex systems-requires population studies

• Obv1. Organisms have great potential fertility, permiting exponential growth of populations
• Obv2. Natural populations remain fairly constant in size, not increasing exponentially
• Obv3. Natural resources are limited
• Inf1. A struggle for existence occurs in a population
• Obv4. Variation occurs among organisms within a population
• Obv5. Variation is heritable
• Inf2. Varying organisms show differential survival and reproduction, favoring advantageous traits-natural selection
• Inf3. Natural selection over many generations gradually produces new adaptations and species

identify essential aspects of reality and remove distracting elements

a trait that evolved by natural selection for a particular biological role

σ_a²=Σ(freq_geno)(g_ai)²

g_ai=sum of avg. excess of all phenotypes involved

how much of the genetic variance can be transmitted to influence the phenotypic variation in the next generation

• 1. Substrate nutrality-reproducting population with heredity and variation
• 2. Underlying mindlessness
• 3. Guranteed results

unreal conditions used to facilitate study eg non-overlap generations, infinite population

avg. excess=Σ(freq_allele)(g_i)

Mayr-A reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature

h_B²=σ_g²/σ_p²

• 1. sexual forms only
• 2. no temporal dimension-BSC is for a slice of time and does not show lineage through time
• 3. not a single unit of evolution-divergence of character does not equal different species
• 4. not practically testable-sexual behavior in lab doesn't always reflect behavior in habitat

• 1. Abstraction and Simplification
• 2. Sufficient Paramaters
• 3. Assumptions

all copies of homologous DNA trace back to a common ancestral molecule

both phenotypes observed when heterozygous eg sickle cell electrophoretic mobility

=(σ_a²)/2

=(h²/2)+[(σ_d²)/(4σ_p²)

• Between X and Y
• =[Cov(X,Y)]/[sqrt(σ_x²σ_y²)]

• between X and Y
• Avg(X-µ_x)(Y-µ_y)

a local population of reproducing individuals that has physical continuity over time and space, lowest biological level that can evolve

diet is the rarer factor of the disease and the genetics is common

• same as non-additive genetic variance in a single locus model
• σ_d²=σ_g²-σ_a² (single locus model)

presence of one allele masks the phenotype of the other eg sickle cell malarial resistance

Phenotype affected by non-genetic forces, which may include other phenotypes within the body eg LDL cholesterol level

• part of non-additive variance in population level arising from inheritance among genotypes at different loci
• when comparing two populations, the rarer genotype shows more additive variance when epistatically correlated

change in allele/gamete frequency in gene pool, fates of alternate forms of genes over space and time ina population

Mutation and Genetic Drift

a trait coopted by natural selection for a role incidental to the trait's origin

σ_p²=σ_g²+σ_e²

rare dispersal across pre existing barrier eg Galapagos

the population of gene copies and potential gametes collectively shared by individuals of a deme

branches show lineal descent of copies of homologous DNA

genetics is the rarer factor of the disease and the diet is common

random changes in allele frequency due to finite number of population size (sampling error), directionless, cumulative, strength is inversely proportional to 1/(2N), rate of losing allele =1/(2N), avgerage time for two genes to coalesce=2N, avgerage time for all genes to coalesce=4N

how much phenotypic variance is associated with genotypic variation in a population in a given generation

σ_g²=Σ(freq_geno)(g_i)²

SNP markers every 10 cM in genome of population, which must have high frequency of phenotype and high linkage disequilibrium

g_i= ^-x^-_pog-^-x^-_pop

less empirical support accumulation of small, quantitative changes leads to qualitative change

branches denote mutational events in the evolutionary histroy of homologous DNA

Set of identical haploid genomes for a specified unit of measurement (same as allele for measurements taken at DNA/chromosomal level) In common usage-bases present at polymorphic sites genotypically linked on a DNA molecule eg SNPs RFLPs

large phenotypic change in a single generation eg Ancon sheep

replication without mutation, refering to alleles and associated phenotypes eg mitochondrial DNA

• µ (or ^-x^- for a sample population)
• (x₁+x₂+...+x_n)/n

not sufficient for epistatic variance at population level

DNA can replicate, can mutate and recombine, encodes RNA/proteins that interact with environmental conditions to influence a phenotype

• µ unitless
• # newly mutated copies
• total # copies of homologous DNA

mutation produced lethal alleles and selection removes them

causes many small changes

h²=σ_a²/σ_p²

• a population based mechanism of evolutionary change invoked to explain adaptation
• Not a random process
• Random component-variation is produced at random with respect to organism's needs
• Non-random component-organisms with favorable traits have higher rates of survival and reproduction, causing populations to accumulate the most favorable variants and discard less favorable ones

• 1. Single locus model=σ_d²
• 2. Multilocus model=σ_d²+σ_epistatic²

Larson disagrees geographic isolation does not precede evolution of species

set of phenotypes associated witha particular genotype in interacton with a variety of environmental conditions and genetic backgrounds

heterozygote phenotype is more fit than phenotype of either homozygote eg sickle cell heterozygote viability in malarial environment

measures heritability without measuring genotype

any measurable trait, either discrete or continuous

Carcraft-A lineage of ancestor-descendant populations diagnosably distinct by divergence of character

Hate group that wants to prove that black people are genetically inferior

Ronald Fisher-multiple loci contribute to the phenotype

hybrid invariability, hybrid sterility, hybrid breakdown

temporal, ecological, behavioral, mechanical, gametic

later forms are superior to early ones in a general sense

analysis of genetic variance for continuously varying phenotypes within a population

• locus whose variation contributes to population variation of a continuously varying phenotype
• found using genome scan followed by tree scan

mutations can be good or bad

phenotype only observed when homozygous eg sickle cell severe anemia

controversial selection on hybrids with postzygotic barriers leads to prezygotic barriers

Phenotype is the result of only one locus

vicariance and founder event

minimum mumber of summary variables, combining relevent information of many parameters at lower levels eg "fitness"

multiple species lineages generated from an ancestor in an undivided geographic area

• haplotype tree used to test SNP sites for influence on the phenotype
• group all haplotypes on either side of a particular branch, call them A₁ and A₂, measure norms of reaction for the resulting genotypes A₁A₁, A₁A₂, A₂A₂, repeat for all branches in tree

• σ² (or s² for a sample population)
• σ²=[(x₁-µ)²+(x₂-µ)²+...+(x_n-µ)²]/n
• s²=[(x₁-^-x^-)²+(x₂-^-x^-)²+...+(x_n-^-x^-)²]/(n-1)

subdivide formerly continuous habitat