5.2: The Law of Independent Assortment
Dihybrid cross involves parent organisms with different forms of two traits.
To determine the F1 generation, you will use a 16 grid Punnett square to solve the probability of
outcomes.
The Law if Independent Assortment states:
a) Each pair of Alleles segregates (assorts) independently of the other pairs during meiosis.
b) All possible combinations of alleles can occur in the gametes. (FOIL method)
Each parent cell has four chromosomes: two alleles for seed colour (yellow or green) are on one set of
homologous chromosomes and two alleles for seed shape (round or wrinkled) are on another pair of
homologous chromosomes. When homologous chromosomes separate during meiosis I, they segregate.
Each cell beginning meiosis II has only one allele for each trait. Also, independent assortment occurs.
The homologous chromosomes line up randomly at the metaphase plate (equator); therefore, the
homologous chromosomes, and the alleles they carry, segregate independently during gamete
formation. Each gamete has two chromosomes: one allele for seed colour is on one chromosome and
one allele for seed shape is on the other chromosome. All combinations of these two alleles are possible
in the gametes: RY, Ry, rY, and ry.