Tuesday, January 27, 2009

Tuesday 1/27

  • Notes on 6.5
  • Practice Doing Punnett Squares
  • Homework: Read 6.5, 6.6
Good job everyone who demonstrated Punnett Squares today!

Punnett Square:
  • Grid system for predicting all possible genotypes resulting from a cross.
    Axes: the possible gametesof each parent.
    Boxes: show thepossible genotypesof the offspring.

Monohybrid cross: involves one trait.(Mono=one, hybrid=combination)

  • Homozygous dominant x Homozygous recessive
    Offspring: all heterozygous, all dominant
  • Heterozygous x Heterozygous
    Genotypes: 1:2:1
    1 homozygous dominant: 2 heterozygous: 1 homozygous recessive
    Phenotypes: 3:1 dominant:recessive
  • Heterozygous x Homozygous Recessive:
    Genotypes: 1:1, heterozygous : homozygous recessive
    Phenotypes: 1:1, dominant : recessive

Dihybrid cross: two traits.

•Mendel’s dihybrid crosses with heterozygous plants yielded a 9:3:3:1 phenotypic ratio.

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