Mendelian, continued

The Dihybrid Cross

• a cross involving two traits
• mating of F-1 individuals from the P-1 cross of two different pure bred lines

dihybrid, no dominance

dihybrid, with dominance

non-Mendelian Genetics

Quantitative traits

• exhibit range of phenotypes
• typically have more than three genotypes
• typically dramatically influenced by environment

Polyploidy

• autopolyploidy
  • following Meiosis, cytokinesis suppressed
  • telophase reforms single nucleus
  • cell resumes Life Cycle at G-1
    with 2n single-chromatid chromosomes
  • at S-1, DNA replication → 2n chromosomes with paired chromatids,
    or, 4n chromatids.
  • after G-2, Meiosis/cytokinesis → 4 gametes with 2n chromosomes each
  • fertilization → 4n zygote
• for quantitative traits, number of genotypes = 2n + 1
  • n = 5;
    2n + 1 = 11 genotypes
  • autoploidy → n = 10;
    2n + 1 = 21 genotypes

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