Lecture 5 - Binomial Equation and Dihybrid cross

• What does n represent in the binomial equation?

  The total number of outcomes
• What does x represent in the binomial equation?

  The total number of unaffected
• What does y represent in the binomial equation?

  The total number of affected
• What do p and q represent in the binomial equation?

  They are both probabilities
• Mendel's Principle of Independent Assortment

  Alleles for 2 traits on different pairs of chromosomes assort independently from one another. Occur during Anaphase I of the meiotic cycle. Where 8 total gametes are produced but there are 4 genotypes or 4 different gametes (duplicates of each)
• The dihybrid cross will generate F1 parents that are heterozygous at each locus: Rr at the shape locus and Yy at the colour locus
• Each F1 parent will generate 4 kinds of haploid gametes (RY; ry: Ry: rY)
• We can use a punnett square to determine the phenotypes and genotypes of offspring. But a punnett square would be unruly with more than 2 genes.
• We can use the probability rule to determine the phenotypes and genotypes of offspring because of the law Independent assortment, we can break down multi-gene crosses into the easy monohybrid cross
• Since a heterozygote may have the same phenotype as the homozygous dominant, a test cross may be performed to determine the individuals genotype
• In a test cross, the individual of unknown genotype must be crossed with a homozygous recessive individual