Final answer:
The expected phenotype ratio from a dihybrid cross is 9:3:3:1, but deviations can occur due to factors like genetic linkage or environmental influences. In hybridization experiments, conditions such as temperature and pressure are standardized to ensure accurate results. Phenotype-gentotype differences were demonstrated by Mendel's hybridization experiments.
Step-by-step explanation:
In Mendelian genetics, the expected phenotype ratio resulting from a dihybrid cross is 9:3:3:1. This ratio presumes that both genes assort independently and that each allele has an equal chance of being transmitted to the progeny. In the shepherd's-purse plant, the observed ratio differs due to genetic linkage or other genetic interactions that alter the independent assortment of alleles.
Factors such as dominance, epistasis, or environmental influences can also cause deviations from expected Mendelian ratios. In hybridization experiments, conditions like temperature and air pressure are standardized to maintain consistency and accuracy of results. This is crucial because the physical environment can impact how genes are expressed and, consequently, the phenotypes observed.
Furthermore, in his hybridization experiments, Mendel showed how the observable traits (phenotype) could differ from the genetic makeup (genotype). For instance, crossing plants with yellow pods and green pods may result in all F1 offspring with green pods (phenotype), though their genotype includes alleles for both pod colors. The reoccurrence of the yellow pod phenotype in the F2 generation confirms the presence of the yellow allele in the genotype of F1 plants.