For a dihybrid cross, we ask students to predict the [F.
Mathematical concept in dihybrid tests for predicting phenotypes of seeds.
Virgin females (designated by a Venus symbol combined with a "V") may be either dihybrid (A or B) or trihybrid (C or D).
Four possible exercises are presented: two dihybrid testcrosses (Figure 2A,B) and two trihybrid testcrosses (Figure 2 C,D).
The second feature about Drosophila that has limited the use of dihybrid
linkage studies of genes on the autosomes arises out of the fact that recombination in males of Drosophila melanogaster is totally suppressed.
However, most genetics investigations with Drosophila analyze offspring patterns of the F2 generation of dihybrid
crosses to determine that genes are linked but do not calculate the map units between the linked genes (College Board, 2001; Mertens & Hammersmith, 2007; Scott, 2001).
While Punnett squares are a useful device for determining the outcome of genetic crosses, they can become cumbersome for dihybrid
or trihybrid crosses.
The fruit fly cross is a dihybrid
cross involving two traits, each trait encoded by a single gene, each gene being represented by two alleles in that specific cross.
National Association of Biology Teachers (1994) and National Academy of Sciences (1998) offer activities or suggestions for using fruit flies, "red wiggler" worms, bacteria, fungi, plant proteins, and dihybrid
crosses of plants.
After learning about meiosis, including the random metaphase alignment of chromosomes, monohybrid crosses, use of Punnett squares, and Gregor Mendel's Theory of Segregation, introduce students to dihybrid
crosses involving two independently assorting genes.