A. Mendel in his experiments used two true breeding plants that only express one particular trait. He would chose plants with different versions of the trait and cross pollinate them. So, in this case, Mendel’ s P generation would be:
P: GGWW x ggww
B. The possible gametes produced by these first or original parent plants (GGWW and ggww genotypes of the parents) are:
GW and gw. When an organism makes gametes, each gamete receives just one copy of the gene, which is selected randomly (Mendel’s law of segregation).
C. If the gametes GW and gw are joined, the genotype in the offspring would be GgWw. This is dihybrid organism because it is heterozygous (have two different allelss, one recessive, one dominant) at two different genetic loci, G and W. The offspring represents the F1 generation.
D. If the individuals with the genotype GgWw are crossed with the individuals with the same genotype (GgWw), the possible gametes are GW, Gw, gW, gw. The possible genotypes for the F2 generation are: GGWW, GGWw, GgWW, GgWw, GGww, Ggww, ggWW, ggWw and ggww. There are nine different genorypes. The genotypic ratio is 1:2:2:1:4:1:2:2:1.
E. F2 generation of offspring of this dihybrid cross has a 9:3:3:1 phenotype ratio. Mendel did similar experiment with his plants and conluded that the pairs of traits in the parental generation (P generation) sorted independently from one another, from one generation to the next.
