Population genetics.txt

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Population genetics.txt
2011-11-06 15:27:46
population genetics

pop genetics
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  1. organelle genetics
    • extra nuclear inheritance
    • traits conditioned by genomes OTHER than nuclear one
    • these genes are called CYTOPLASMIC genes - they arise in organelles such as mitochondria or plastids
  2. Maternal inheritance
    • Organelles contributed to zygota via EGG, not sperm:
    • 1. chloroplasts or
    • 2. mitochondria inherited from MOTHER
  3. Maternal inheritance
    • Genotype of mother determines phenotype of progeny
    • ie snail shells: coiling dominant to maternal - mother's trait present in every offspring
    • in a diagram, mother's circle will be shaded in every case
  4. X inactivation & Barr bodies
    • XX: one female X chromosome in each cell is inactivated
    • During development remains inactivated
    • In diff development lineages, a different X becomes inactivated
    • 1st recog. by Mary Lyon
  5. Lyon's hypothesis
    • 1. Females have a chromatin body in interphase nucleus, but not in males
    • 2. Female cats are mosaic for coat color on gene X (calico cats), human (anhidrotic ectodermal dysplasia, red-green color blindness)
    • w/colorblindness, XR Xr, although every cell can't see color, as long as you have some of both you won't be colorblind.
    • 3. Female mice w/a translocation b/w X and an autosome w/a coat color gene are MOSAIC
  6. quantitative genetics
    • continuous traits showing a distribution of phenotypes
    • continuous traits are affected by many genes and are also called POLYGENIC or MULTIGENIC traits
  7. Quantitative Traits
    • 1. Matings b/w extremes in phenotypes will usually result in INTERMEDIATE phenotype (usually occurs when both parents are homozygous for different sets of alleles affecting different characteristics) - ie AA x aa = Aa (tall x short = medium HEIGHT)
    • 2. Matings b/w intermediate phenotypes can result in F1 outside the range of parents. (produce progeny from one extreme to the other & in between)
  8. Transgression
    Phenomenon that progeny can be OUTSIDE the range of the two parents for a particular trait. ie 8ft tall child from 2 tall parents
  9. Frequency distribution
    • includes Mean and Variance to analyze polygenic traits
    • Mean: sum of sample measures / n
    • n = # in sample
    • Variance: s^2 = (mean - x)^2 / n-1
    • x = number ur looking at
    • Standard Deviation: Square root of Variance
  10. Variance facts
    • 1. If variance increases from F1 to F2, Multiple genes are involved.
    • 2. Magnitude of increase gives indication of how many genes
    • if only a FEW genes, Variance will increase A LOT
    • if MORE genes, Variance will increase LESS
    • Prob of a few genes getting to extremes is HIGHER than lots of genes getting to extremes
  11. Heritable
    if offspring resemble parents as result of genetic similarity
  12. Heritability
    • Has both an environmental VS genetic component
    • ie - environmental can be improper nutrition leading to less growth
  13. Population Genetics
    Study of genes in population of a species w/regards to allele freq and how they change
  14. Gene pool
    Shared genes in a population
  15. Hardy-Weinberg Law
    • Test of assumptions about a population
    • Allows calculation of genotypic frequencies from allele freq. (and vice versa)
    • Need to hold the following true:
    • 1. Organisms are diploid
    • 2. Reproduction is Sexual
    • 3. Large populations
    • 4. Random mating
    • 5. No evolutionary forces, no mutations, no migration, no natural selection
    • p^2 + 2pq + q^2 = 1
  16. Nonrandom Mating
    • Positive assortment mapping: individuals w/similar phenotypes mate preferentially. (ie humans and height)
    • Negative assortment mapping: phenotypically dissimilar individuals mate more often than at random
    • Rare male advantage: in fruit flies, an UNUSUAL phenotypic male will be selected by females more often than at random (ie guitar playing band member syndrome)
    • Inbreeding: mating among relatives increases homozygosity at expense of heterozygosity. Progeny is small in populations...Makes detrimental mutations homozygous
    • Outbreeding: mating b/w non-related individuals. Maintains detrimental mutations heterozygous, but if no mates in small population, no progeny.
  17. Fitness
    Ability to pass on genes
  18. Principles of EVOLUTIONARY genetics
    • 1. new genes come from gene duplication
    • 2. new alleles come from MUTATION
    • 3. Allele freq can change by selection, migration, or in small population, genetic drift
    • 4. Genotypic freq can change by in/outbreeding, assortive mating
  19. Natural selection
    • Can change allele freq thru SEXual selection and environmental factors (migration)
    • or can be done through Human selection (ie humans select dogs for pure breeding)