Final answer:
The expected phenotypic ratio in the offspring of a cross between two parents heterozygous for the WT long-wing phenotype (Gg) is 3:1, with three-quarters expressing the dominant long-wing phenotype and one-quarter expressing the recessive phenotype.
Step-by-step explanation:
Phenotypic Ratios in Offspring of a Monohybrid Cross When two parents are heterozygous for the WT long-wing phenotype (Gg), the expected phenotypic ratios in the offspring can be calculated using a Punnett square. The genotypes of the parents (Gg × Gg) result in a phenotypic ratio of 3:1, where 'G' represents the dominant allele for the long-wing phenotype and 'g' represents the recessive allele. This means in a large enough sample size, three quarters of the offspring are expected to have the long-wing phenotype (GG or Gg), and one quarter are expected to have the alternate phenotype (gg). The application of the Punnett square to predict offspring genotypes shows that 25 percent of the offspring will be homozygous dominant (GG), 50 percent will be heterozygous (Gg), and 25 percent will be homozygous recessive (gg). This genotypic ratio directly correlates with the phenotypic expression due to dominance. Therefore, the phenotypic ratio of the offspring will be predominantly the long-wing phenotype, which is dominant.