Mendelian Genetics I: Dominant and Recessive Genetic Factors

  1. a.      Explanation of heredity most widely in favor= __
    blending hypothesis
  2. Explain the blending hypothesis
    •                                                               i.      Genetic material contributed by two parents mixes in manner similar to paint
    • 1.      Predicts that freely mating population will give rise to uniform population of individuals
  3. particulate hypothesis
    •                                                               i.      Gene idea
    •                                                             ii.      Parents pass on discrete heritable units—genes—that retain their separate identities in offspring

  4. a.      __ documented __mechanism for inheritance
    b.      Use of Garden Peas
                                                                  i.      Encouraged by strong professors to become scientists
    1.      Christian Doppler: experimentation/ trained Mendel to use math to help explain natural phenomena
    2.      Franz Unger: aroused Mendel’s interest in causes of variation in plants
    • Gregor Mendel
    • particulate

  5.                                                               i.      Began breeding garden peas to study __
    Why peas?
    • inheritance
    • 1.      Large variety
    • 2.      Short generation time and large number of offspring from each mating
    • 3.      Strict control of mating

  6. 1.      Large variety
    a.      Hereditable feature that varies among individuals= __
    b.      Variant of character= __
    • character
    • trait
  7. Strict control of __
    a.    Reproductive organs of pea plant in flowers, and each pea flower has both __ and __
    b.    Usually __
    i.    To __, he removed immature stamens before pollination could occur and dusted pollen from another plant onto altered flowers
    1.    Resulting zygote: developed into plant embryo encased in seed (pea)
    • mating
    • pollen-producing organs (stamens) and egg-bearing organs (carpels)
    • self-fertilize
    • cross-fertilize

  8.                                                               i.      Mendel only tracked characters that occurred in __ different forms
    1.      Ex: purple or white flowers, no intermediate
                                                                ii.      Also, used __ plants
    1.      What are they?
    • two
    • true-breeding
    • varieties that, over many generations of self-pollination, produced same variety as parent cell
  9. i.    Typical breeding Experiment
    1.    Cross-pollinated two contrasting, __pea varieties
    a.    __, or crossing, of two true-breeding parents is __
    i.    Parents: __ generation
    1.    Hybrid offspring:__
    a.    Their hybrid offspring
    i.    __
    • true-breeding
    • Mating
    • hybridization
    • P
    • F1
    • F2
  10. ii.    Mendel’s quantitative analysis of the F2 plants from thousands of genetic crosses allowed him to deduce two fundamental principles of heredity:
    1.    __ and __
    Law of segregation and law of independent assortment
  11. b.    Law of Segregation
    i.    All F1 offspring had what color flowers?
    1.    White appeared in __generation
    2.    __ ratio in F2 ratio
    ii.    Heritable factor for white flowers did not disappear in F1 plants, but was __, when purple-flower factor present
    1.    Purple flower: __
    2.    White: __
    • second, F2,
    • 3:1
    • just as purple as purple-flowered parents
    • hidden or masked
    • dominant
    • recessive
  12. iii.    Mendel’s model
    1.    __related concepts making up his model, the fourth which is the__
    • Four
    • law of segregation
  13. What are his related concepts?
    • a.    Alternative versions of genes account for variations in inherited characters
    • i.    Alternative versions= alleles
    • b.    For each character, an organism inherits two copies of a gene, one from each parent
    • c.    If two alleles at locus differ, the dominant allele determines the organism’s appearance; the recessive has no noticeable effect on the organism’s appearance
    • d.    Law of Segregation: two alleles for a heritable character segregate during gamete formation and end up in different gametes
  14. i.    Genetic __represented __in diploid cell, once on each __of a specific pair of chromosomes
    1.    Two __at locus may be identical or different
    • locus
    • twice
    • homolog
    • alleles
  15. iv.    __: handy diagrammatic device for predicting allele composition of offspring form a cross between individuals of known genetic makeup
    1.    Capital letter: __
    2.    Lowercase: __
    • Punnett Square
    • dominant
    • recessive
  16. 1.    Organism with pair of identical alleles for character: __
    a.    Parental generation, the purple plea plant was __for dominant (PP) allele, while white is __for recessive (pp) allele
    • homozygous
    • homozygous
    • homozygous
  17. 2.    Organism with two different alleles for gene is __
    a.    Produce gametes with different alleles, so not __
    3.    Because of this, organism’s traits don’t always reveal genetic composition
    a.    Appearance and physiological traits: __
    b.    Genetic makeup: __
    • heterozygous
    • true-breeders
    • phenotype
    • genotype

  18.                                                               i.      Test Cross
    •                                                               i.      Test Cross
    • 1.      If we have a mystery pea plant with purple flowers and want to know whether it is homo or heterozygous, we cross it with a white plant, which will make only gametes with recessive allele
    • a.      Allele in gamete contributed by mystery plant will determine appearance
  19. Results of Test Cross
    •                                                                                                                                       i.      If homozygous dominant, it will result in an all-purple F1 generation
    •                                                                                                                                     ii.      If heterozygous, the offspring will be 1:1 ratio, both purple and white
  20. 1.    All F1 progeny produced in crosses of true-breeding parents were __, meaning they were heterozygous for one particular character being followed= __
    2.    Mendel followed two characters at same time= __= __
    • monohybrids
    • monohybrid cross
    • dihydrbids
    • dihybrid cross
  21. 3.    Will separate characters stay together?
    4.    In F2 offspring, the hybrids do not transmit alleles in same combinations in which the alleles were inherited from P generation
    a.    If this did occur, what would it result in?
    • not always
    • This would result in the F1 hybrids producing only two classes of gametes= dependent assortment= rejected
  22. 5.    Two pairs of alleles segregate __of each other
    a.    Genes packaged into gametes in all possible allelic combinations
    i.   __ ratio for dihybrid cross
    1.    16 probable ways to combine
    • independently
    • 9:3:3:1
  23. Law of Independent Assortment
    each pair of alleles segregates independently of each other pair of alleles during gamete formation
  24. The Law of Independent Assortment applies only to __
    genes on different chromosomes—on nonhomologous chromosomes—or very far apart on same chromosome
Card Set
Mendelian Genetics I: Dominant and Recessive Genetic Factors