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2014-12-21 14:41:48
genetics section chads videos for OAT
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  1. genotype
    the genetic makeup responsible for a particular trait
  2. Phenotype
    an organism’s observable traits (determined by genotype and environment)
  3. gene
    genetic material coding for a single gene product (peptide, rRNA or tRNA)
  4. locus
    the chromosomal location of a gene
  5. allele
    one variant of a gene
  6. Homologous chromosomes
    • – chromosomes that code for the same set of genes
    • - may have different alleles though (one from each parent)
  7. Homozygous
    – having two identical alleles for a gene
  8. Heterozygous
    – having two different alleles for a gene
  9. wild type
    the “normal” or most prevalent allele in a population
  10. dominant
    an allele where only one copy is necessary to yield the corresponding phenotype
  11. recessive
    an allele where two copies are necessary to yield the corresponding phenotype
  12. complete dominance
    when a heterozygote has the phenotype of only 1 of the alleles (the dominant one)
  13. codominance
    both inherited alleles are completely expressed (ex. blood types – ABO)
  14. incomplete dominance
    – phenotypes of the progeny that are intermediate of the parental phenotypes(snap dragons – homozygous red crossed with homozygous white gives pink progeny)
  15. leakage
    when a loss of function mutation doesn’t result in complete lack of a phenotype
  16. Penetrance
    the percentage of organisms having a certain genotype expressing a certain phenotype
  17. expressivity
    a term describing the variation in phenotype among organisms with a given genotype
  18. Pleiotropism
    when a single gene affects multiple traits
  19. Polygenism
    when multiple genes affect a single trait
  20. epistasis
    when the expression of a gene is dependent upon another gene
  21. gene pool
    the set of all alleles in a population
  22. Nondisjunction
    – failure of tetrads to separate during meiosis I or sister chromatids in meiosis II

    • Examples: Down Syndrome (trisomy 21), Turner Syndrome (X),
    • Kleinfelter Syndrome (XXY)
  23. translocation
    movement of a segment of one chromosome to another non-homologous chromosome

    (ex. Down syndrome – chromosome 21  14)
  24. Law of segregation
    – separation of alleles into haploid gametes
  25. Law of independent assortment
    – genes assort independently to the progeny
  26. Recombination (single and double crossovers)
    • exchange of segments from homologous chromosomes
    • -leads to new combinations of alleles
    • -occurs during prophase I of meiosis