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Exam 4, One of the three principles, Dihybrid vs Monohybrid …

- - - - Each homolog is from a different parent
      - Homologous chromosomes
      - Interactions of genes on each sets of chromosomes determines the genetic characteristics
      - Each chromosome has a partner
      - Resemble each other in size, shape & hereditary information
    - - In general, the possibilities are 2n
        
        246 = 7.04 x 1013
        
        Ex: human with 46 chromosomes
      - During Metaphase II
        
        Orientation of sister chromatids is random
      - During Metaphase I
        
        Orientation of bivalents is random
      - Crossing over
        
        Synaptonemal complex forms
        
        Mixes the genes present in homologous chromosomes
        
        During Prophase I
        
        Results in new combinations not present in the chromosomes of the parental cells
        
        Usually at least one chiasma occurs between every pair of homologous chromosomes
    - - Promotes heterozygosity
      - Advantages include
        
        Bet-hedging to novel environments
        
        Multiple deleterious alleles can be bunched together and eliminated
        
        genetic diversity
        
        Escape host-parasite negative impacts
      - New combination of alleles from each parent
      - Pollination
        
        Cross pollination
        
        Self pollination
  - - - Segregation
      - Independent Assortment
      - Dominance
    - - Genotype is made up of alleles
      - Phenotypes determined by these alleles (and the environment)
      - Each individual has a unique genotype
      - There is no guarantee that an allele will manifest
        
        Heterozygosity
        
        One of 2 genes (dominant allele) has a detectable effect on an organism's appearance
        
        The other gene has no discernable effect (recessive allele)
        
        Homozygosity, both alleles are the same
      - Principle of Segregation
        
        Offspring inherit 2 alleles for a gene
        
        One from each parent
        
        Inherit a homologous chromosome
        
        During meiosis, 2 members of a gene pair separate from each other
        
        Each gamete contains only one allele for each gene
        
        Each gamete has an equal chance to inherit either one of the genes
        
        Alleles are segregated, separated, from one another during meiosis
    - - Visual representation of the offspring inheritance patterns
      - Monohybrid is a cross between 2 homozygous parents with different alleles.
      - Punnett square
        #
    - - Gene pairs that are not linked segregate independently
      - Evidence provided from a dihybrid cross
        
        3:1 phenotypic ratio for each of the 2 alleles
      - Gene pairs that are not related (homologs) segregate independently
    - - Parental
        
        Homozygous
        
        True breeding
      - F1
        
        First filial generation
        
        Heterozygotes
      - For reference
      - Genotypic ratio
        
        Allele combinations
      - Same as previous video
      - Phenotypic ratio
        
        Trait combinations
  - - - Snapdragons
        
        Red x white = pink
      - Phenotype of heterozygote is intermediate between those of parent homozygotes
    - - Punnett square theoretical crossing works similar
      - Breeding experiments to determine dominance
      - Many populations have more than 2 alleles for a particular locus
      - Figuring out alleles is complex
    - - Point mutation
        
        Single nucleotide change
      - Chromosome mutation
        
        Duplication
        
        Part of the chromosome has doubled
        
        Inversion
        
        Piece rotates 180
        
        Deletion
        
        Segments of chromosome are lost
        
        Translocation
        
        Exchange of parts between 2 nonhomologous chromosomes
        
        Transposons
        
        Jumping genes
        
        Movable genetic element
      - Changes in the genetic makeup of an individual
    - - Chromosome inherited same as parent
      - Only 2 gamete types possible rather than 4
      - Fail to mix alleles across homologs
    - - Phenotype is cumulative result of combined effects of many genes
      - Example abscisic acid
      - Multiple genes for one character
      - Most traits
      - Continuous variation
      - Populations tend to have normal distribution
    - - May interfere or mask
      - Ex: digitalis petal color
        
        One gene impacts red intensity
        
        d light red
        
        D dark red
        
        Pigment location
        
        w throughout corolla
        
        W spots of nectar guide
      - One gene interacts with another
    - - 4 haploid genotypes
      - Not produced in equal numbers
        
        Parentals more abundant
        
        Recombinants less abundant
    - - Inheritance of a single gene which visibly influences several traits
      - Ex: awn of wheat
        
        Wheat with awns have greater yield than those without awns
      - Single gene with multiple effects on the phenotype
    - - Selfer
        
        Flower early
        
        Seasonal drought
        
        Small petals
        
        Physiologically escape?
      - Outcrosser
        
        Flower late
        
        Seasonal drought
        
        Large petals
        
        Physiologically tolerant?
    - - Autopolyploid
        
        Failed meiosis
        
        Self fertilization
      - Allopolyploid
        
        Mismatch during mating
        
        Second mating creates matched pairs
        
        Meiotic error
      - Having more than two copies (2n) of a chromosome
      - Polyploid example
        
        Original ancestral species had 14 chromosomes
        
        Durum wheat
        
        Tetraploid
        
        pasta
        
        28 chromosome
        
        Result of sequential hybrid doubling and quadrupling
        
        Bread wheat
        
        42 chromosome
        
        Hexaploid
        
        Gluten for lofty bread
        
        Wheat
      - Evolutionary significance
        
        Relax selection pressure
        
        Accumulate mutations that eventually result in beneficial trait
        
        2 groups of ancient duplications
        
        Common ancestor of seed plants
        
        Common ancestor of extant angiosperms
        
        Polyploid mask deleterious recessive alleles
- - - - All of the alleles of every gene in a population make up the gene pool
      - A population is a group of individuals of the same species that occupy the same region and can interbreed with each other
      - Gene Pool: Allele & Genotype Relative frequencies
        
        Allele frequency
        
        Number of copies of an allele in a population divided by the total number of alleles for that gene in a population
        
        Genotype frequency
        
        Number of individuals with a particular genotype in a population divided by the total number of individuals in a population
      - Allele Relative Frequency
        
        Divided by
        
        The total number of all alleles for that gene in a population
        
        Number of copies of an allele in a population
      - Genotype Relative Frequency
        
        Divided by
        
        The total number of all individuals in a population
        
        Number of individuals with a particular genotype in a population
      - Hardy-Weinberg equation
        
        predicts an equilibrium-unchanging allele and genotype frequencies from generation to generation-if certain conditions exist in a population and provides a quantitative relationship between the allele and genotype frequencies
        
        No new mutations
        
        No genetic drift. The population is so large allele frequencies do not change due to random sampling effects
        
        No migration
        
        No natural selection
        
        Random mating
        
        HW equations
        
        If, instead, we always use p and q rather than choosing an upper and lowercase letter to represent alleles:
        
        Thus p+q=1
        
        Therefore (p+q)2=12;
        
        The frequency of the recessive allele is represented by q
        
        And p2+2pq+q2=1
        
        The frequency of the dominant allele is represented by p
        
        p2= genotypic frequency of RR
        
        q2= genotypic frequency of rr
        
        2pq= genotypic frequency of Rr
      - HW vs Punnett
        
        The frequency of gametes carrying a particular allele is equal to the allele frequency for a population in Hardy-Weinberg equilibrium.
        
        Multiplying the allele frequencies gives the proportion of each allele combination in the population.
  - - - Changes in a population’s gene pool from generation to generation
      - Factors
        
        Mutation
        
        Natural selection
        
        Genetic drift
        
        Nonrandom mating
        
        Migration
    - - Some are apparent in phenotype
      - Source of all new alleles
      - Change in one of the nucleic acids
      - Must be in gametes to be inherited
        
        Female ovule egg
        
        Male pollen sperm
    - - Example: Aquilegia
      - Color variation
      - Polymorph = many phenotypes in a population
      - Spur-length variation
      - Dimorphic
        
        2 phenotypes
        
        Dominant-recessive systems
      - Can be due to a single nucleotide polymorphism
    - - Acts most strongly in small populations relative to large
      - Bottleneck effect
        
        Large population diminished suddenly
        
        Natural catastrophe
        
        Migration
        
        May increase in size again but unlikely to regain original diversity
      - Random loss of alleles
    - - Pollinator vectors
        
        Pollination syndromes
      - Some of the individuals reproduce more than others
        
        Based on individual phenotypes
      - Plants “choose” their mates
    - - Male-male competition
        
        Excess of pollen grains
        
        Pollen tubes can interfere with one another
      - Female choice
        
        Barriers on stigma surface preventing germination
    - - Can be impeded by
        
        The environment
        
        Life history
      - Repercussions for
        
        GMO and
        
        speciation
        
        climate change
      - Movement of alleles into and out of a population
        
        Immigration
        
        Into
        
        Emigration
        
        Out of
    - - Followed by adaptive radiation
      - Example: Hawaiian lobeliads
      - Bottleneck from long distance dispersal
    - - Over time, individuals with the 2 genotype are able to reproduce more and grow in numbers
      - The overall vigor of the population grows
      - In this example, 2 (triangle) has more vigorous offspring
      - So does population size
      - One allele selectively advantageous
    - - Crop breeders for thousands of years
      - Example Brassica
      - Selection by humans
        
        Increased frequency of desired trait
        
        Elimination of undesired traits
  - - - Differential survival
      - Survival due to phenotypes that are heritable
        
        Phenotype coded by genotype
      - Death does not mean natural selection has occurred
    - - Some alleles may encode proteins that enhance an individual’s survival or reproductive capacity
      - Individuals with beneficial alleles are more likely to survive and reproduce
      - Distinct alleles may encode proteins of differing functions
      - Over the course of many generations, allele frequencies of many different genes may change through natural selection
      - Within a population there is allelic variation arising from various factors such as mutations causing differences in DNA sequences
      - This significantly alters the characteristics of a species
- - - - Exponential growth
        
        J-shaped curve
        
        Unlimited resources
      - Logistic growth
        
        S-shaped curve
        
        Typical of a population that
        
        self regulates
        
        Has a carrying capacity (K)
      - Population size (N)
    - - Result in die off
        
        Limited resources
      - Overshoot K
    - - K = carrying capacity
      - dN/dt = population change over time
      - N = population size
      - Exponential growth
        
        dN over dt equals r times N
      - r = intrinsic growth rate
        
        Relevant for r > 0
      - Logistic growth
        
        dN over dt equals r times N times the quantity one minus N divided by K
    - - Exponential growth
        
        dN/dt = rN
      - Logistic growth
        
        dN/dt = rN[(K-N)/K] =
        
        rN(1-N/K)
    - - r-selected
        
        Weedy
        
        Annuals
        
        Disturbed areas
        
        Little investment in defense
        
        Grow exponentially
        
        Many, small fruits
      - K-selected
        
        Fluctuate around carrying capacity
        
        Fairly stable habitats
        
        Perennials
        
        Invest in defenses
        
        Resource-intensive fruits
    - - Many strategies exist
      - Grime’s model
        
        Disturbance
        
        Biotic
        
        Herbivory
        
        Pathogens
        
        Anthropogenic
        
        Abiotic
        
        Fire
        
        Wind
        
        3 life stages
        
        C- competitors
        
        S- stress tolerators
        
        R- ruderals
        
        Stress
        
        Resource availability
        
        Nutrients
        
        Light
        
        Water
        
        Growth inhibitors
        
        Temperature
        
        Toxins
      - Plants must make trade-offs due to environmental necessities
  - - - lx= proportion of individuals that survive from birth (age 0) to age x;
        
        Nx/N0
      - Fx= average number of offspring born to a female while she is age x
      - Sx= proportion of individuals of age x that survive to age x+1;
        
        Nx+1/Nx
      - lx(Fx) = average number of offspring per capita at age x
      - Nx= number of individuals alive at age x
      - x = age
    - - Dependent on environment
      - Type III, typical of r-selected species
      - Type I, typical of K-selected species
      - Same species can display all 3
      - Visual representation of survivorship
      - How long did individuals survive
    - - Take the log10 of this value
      - Plot against age to produce a figure
      - Take survivorship (lx) and multiply by 1000
      - Example: Type I curve
      - Survivorship curves are plotted logarithmically
  - - - bound together by a shared environment and a network of influence each species has on the other.
      - factors affecting interactions include
        
        abiotic environment
        
        biotic interactions that occur between species
      - a group of actually or potentially interacting species living in the same location.
    - - Facilitation (+/+)
        
        Mutualism
        
        Pollination
        
        Benefits both
      - Commensalism (0/+)
        
        Benefits one, neutral to the other
      - Negative interaction -
      - Amensalism (0/-)
        
        Negative to one & neutral to other
      - Beneficial interactions +
      - Predation (+/-)
        
        Herbivory
        
        Parasitism
      - Range of interactions
      - Competition (-/-)
        
        Both are negatively impacted
        
        Competition for resources
    - - Prey
        
        Positive impact on predator
        
        Negatively impacted by predator
        
        N
      - Population sizes are influenced by each other
      - Predator
        
        Negative impact on prey
        
        Positively impacted by prey
        
        P
    - - dN/dt = population change over time
      - Exponential growth
      - K = carrying capacity
      - Logistic growth
      - N = population size
      - Can similar model predator-prey growth and the impact each has on the other
      - r = intrinsic growth rate
    - - At low prey and predator population sizes, prey increase exponentially
        
        As more food for predators is available, predator survival and reproductive success increases, resulting in predator population growth following that of their prey
        
        As predator populations increase, prey death rate exceeds birth rate, resulting in prey decline
        
        As prey number declines, there is not enough food to sustain a high predator population and thus predator death rate exceeds that of birth rate
    - - dN/dt = rN-aNP
        
        dN/dt=rate of change with time of the prey population
        
        r=intrinsic rate of increase for prey
        
        N=number of prey individuals
        
        a=predator’s per capita attack rate
        
        Number of prey eaten per predator per unit time
        
        P= number of predator individuals
      - dP/dt = faNP-qP
        
        f=constant, indicating predator’s efficiency at converting the prey it has eaten into new predators
        
        q=predator’s per capita mortality rate
        
        dP/dt= rate of change with time of predator population